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Adjacent
The d4 square is adjacent to c4, e4, d3, and d5. In Arimaa, adjacent does not include diagonals, which have no place in the rules.
Arimaa Challenge
The Arimaa Challenge was an annual match between a top bot and top human players; humans dominated for eleven years, until a bot's surprise victory in 2015.
Away trap
An opponent's home trap: c6 and f6 are away traps for Gold, while c3 and f3 are away traps for Silver.
Basket
A basket is like a frame or fence, but does not directly involve a trap square. A piece in a basket is blocked on three sides, and can't escape on the fourth side.
Blockade
A blockaded or smothered piece is surrounded by pieces which it can't push away. A blockaded square is occupied by a piece which can't be pushed off. See also Phalanx, Frame, Immobilization.
Camel
The second strongest of the six unique Arimaa pieces. Each side has one camel.
Capture
A captured piece is removed from the board; a piece is captured when it occupies a trap square with no friendly piece beside it. There are two common ways a piece might be captured: it could be dislodged into an undefended trap, or might already be on a defended trap square which then becomes undefended.
Cat
The fifth strongest of the six unique Arimaa pieces. Each side has two cats.
Dislodge
To push or pull an opponent's piece. Dislodge should not be confused with capture.
Dog
The fourth strongest of the six unique Arimaa pieces. Each side has two dogs.
Draw
Prior to July 1, 2008, one who had lost all eight rabbits could still get a draw by capturing all remaining enemy rabbits. Draws are no longer possible, as a game now ends when one side loses all eight rabbits.
East wing
The right side of the board viewed from Gold's perspective, specifically the f-, g-, and h-files.
Elephant
The strongest of the six unique Arimaa pieces. Each side has one elephant, which is the only piece that cannot be pushed or pulled by the opponent.
Elephant deadlock
The two elephants are deadlocked when both remain next to the same trap, preventing any capture therein.
Elimination
A player wins by elimination if the opponent has no rabbits left. In the rare event that each player loses his last rabbit in the same move, the one who made the move wins. See also Goal, Immobilization.
Endgame
The game phase when a goal line can no longer be blocked reliably, and thus gameplay centers around goal threats. See also Opening, Middlegame.
Exchange
An exchange or trade occurs when each side captures material within a few turns. If each side captures a rabbit, that is a rabbit exchange. If the gold camel is captured and then a silver horse is captured, that is a camel-for-horse exchange. See also Sacrifice.
False protection
When two friendly pieces next to a trap could each be dislodged in two steps, resulting in a capture in an apparently protected trap. See also Mutual protection.
Fence
A fenced piece is stuck next to a trap, and could only step into that trap. A fence may result in a capture, frame, or hostage.
File
One of eight columns on an Arimaa board. From Gold's perspective, the a-file is on the left and the h-file is on the right. From Silver's perspective, it is the reverse.
Flip
In one turn, a piece can pull and then push a weaker enemy piece; the stronger piece finishes where it started, having flipped the enemy piece two squares.
Fork
A forked piece is simultaneously threatened with capture in two different traps. The forked piece would have to be on c4, c5, d3, d6, e3, e6, f4, or f5.
Four-for-two
A four-step move which can be undone in two steps by the opponent. Like three-for-ones, four-for-twos are seldom good moves.
Frame
A piece which is on a trap square, securely surrounded on three sides by opposing pieces, has been framed. Its lone friendly defender is pinned. See also Basket, Phalanx, Blockade.
Freeze
A piece is frozen if no friendly piece occupies an adjacent square, and a stronger enemy piece does occupy one. A frozen piece cannot move until a friendly piece is beside it, or until the stronger enemy piece leaves.
Free piece
A free piece can move around with limited risk. Blockades, frames, hostages, and goal threats may restrict pieces on both sides, leaving other pieces to decide the game. Having the strongest free piece or strongest local piece can be a large advantage.
Friendly piece
For Gold, any gold piece is a friendly piece. For Silver, any silver piece is friendly.
Goal
If a rabbit reaches the opponent's home rank, the game is won by goal, which is the usual way a game ends. See also Elimination, Immobilization.
Gold
Gold is the player with gold pieces. Gold is both the first to set up and the first to move. See also Silver.
Hang
A hanging piece is exposed to immediate capture. See also False protection.
Home trap
A trap on a player's third rank. The squares c3 and f3 are Gold's home traps; the squares c6 and f6 are Silver's home traps. See also Away trap.
Horse
The third strongest of the six unique Arimaa pieces. Each side has two horses.
Hostage
A hostage piece is held near a trap and threatened with capture should a friendly defender leave.
Immobilization
A player wins by immobilization if the opponent has no piece which can move, or if any move the opponent could make would recreate a position they created twice before. See also Blockade, Goal, Elimination.
Key square
A square north, south, east, or west of a trap square.
Lemming
Not recognizing a lost cause, some bots will go all out to save a doomed strong piece. The bot sends over a weak piece to defend it, only to have the weak piece captured with the strong piece no better off. The cycle may repeat several times, with the bot sending over lemmings and the opponent capturing them.
Middlegame
Mutual protection
When two or more pieces adjacent to a trap protect each other from capture by stronger enemy pieces. See also False protection.
Opening
The period from setup roughly until the first capture. See also Middlegame, Endgame.
Overload
An elephant is said to be overloaded if its side faces multiple threats which no other piece can defend against. Other pieces might become overloaded first, causing a ripple effect.
Phalanx
When every square a piece could be pushed onto is already occupied. A phalanx may be part of a larger blockade, or may simply block a particular move.
Pin
A lone friendly piece supporting a framed piece is said to be pinned. If a pinned piece moves, the framed piece disappears instantly.
Pinch
A capture defense in which an enemy piece is surrounded so that it cannot push or pull a piece into a trap.
Postal game
A slow game in which the players are allowed a specified number of hours or days to complete each move. Also known as a correspondence game.
Pull
A piece can pull a weaker enemy piece by first stepping onto an unoccupied adjacent square, and then moving the enemy piece onto the square that was just vacated. A pull requires two steps.
Pull and replace
When a piece pulls a weaker enemy piece, and then a friendly piece steps onto the square the enemy piece was pulled from.
Push
A piece can push a weaker enemy piece by first moving it to an adjacent empty square, and then itself stepping onto the square which that enemy piece had occupied. A push requires two steps. A phalanx may block a push.
Push and replace
When one piece pushes another and steps away, allowing a different friendly piece to take a square formerly occupied by an enemy piece. See also Pull and replace.
Quadrant
A quarter of the board (16 squares), distinguished by compass directions from the perspective of Gold. The northwest quadrant contains the c6 trap, the northeast contains f6, the southwest contains c3, and the southeast contains f3.
Rabbit
The weakest unit on the board, and the only piece that cannot move backwards. Each player starts with eight rabbits, and aims to eventually get one to goal.
Rank
One of eight rows on an Arimaa board. Gold begins the game with 16 pieces on the first and second ranks, while Silver begins with 16 pieces on the seventh and eighth ranks. The home rank for Gold is 1, while Silver's is 8.
Repetition rule
A player who has created the same position twice may never create that exact position again. This is a consideration in sequences where players undo each other's moves.
Rotation
When a piece holding a blockade or frame is replaced by a weaker piece or a phalanx, the original piece has rotated out. If a hostage defender is replaced, usually by multiple weaker pieces, the original defender has rotated out. A piece can likewise rotate out of a trap control fight. See also Swarm.
Sacrifice
A strong piece might be sacrificed so that a friendly rabbit can reach goal. A weak piece might be sacrificed while one secures a frame or hostage. Likewise, one might have to give up a piece to break an elephant blockade or stop an enemy goal.
Scatter
When a player's home trap is invaded, nearby pieces may scatter to avoid capture.
Setup
The first turns of the game, when Gold arranges his pieces on the first and second ranks, and then Silver arranges her pieces on the seventh and eighth ranks.
Silver
Silver is the player with silver pieces. Silver is second to set up and second to move. See also Gold.
Step
A piece can step onto any unoccupied adjacent square. A player takes one to four steps on any turn. Any piece move requires one step; a push or pull uses two steps, since two different pieces move.
Strength
There are six unique types of pieces, each with a different strength. A piece can push, pull, or freeze any weaker enemy piece. From strongest to weakest, the units are elephant, camel, horse, dog, cat, and rabbit.
Strong piece
The elephants, camels, and horses are sometimes known as strong pieces. When one side loses two such pieces, an opposing dog might then be considered a strong piece, as it faces threats from only two enemy pieces.
Swarm
When several pieces advance toward an away trap. A swarm may allow an advanced elephant to rotate out of a trap control fight, or out of hostage defense.
Three-for-one
When a piece takes a step and then returns to its original square while pulling a piece, and the pulled piece is neither blocked nor frozen, those three steps can be undone in a single step by the opponent. If this in fact happens, those three steps gave away time.
Three-for-three
Three steps which could be undone in three steps by the opponent. When three steps cancel three steps, both sides have effectively taken zero- or one-step turns. This may continue for several turns, as long as the fourth steps sometimes create unique positions.
Trap
There are four trap squares on the board, located at c3, c6, f3 and f6. A piece can be captured in a trap square.
Turn
A player completes a turn by moving pieces a total of one, two, three or four legal steps. The opposing player then gets a turn. Also known as a move.
West wing
The left side of the board viewed from Gold's perspective, specifically the a-, b-, and c-files.