telltale

From tell +‎ tale.

• tell-tale
• tell tale

telltale (plural telltales)

1. One who divulges private information with intent to hurt others.

   Synonyms: blabbermouth, gossip, rumormonger, talebearer; see also Thesaurus:gossiper

   • 1596-97, William Shakespeare, The Merchant of Venice, Act V, Scene i:

     PORTIA:

     No note at all of our being absence hence;

     Nor you, Lorenzo; Jessica, nor you.

     LORENZO:

     Your husband is at hand; I hear his trumpet:

     We are not tell-tales, madam; fear you not.

2. (chiefly US, slang) Tattletale; squealer.
3. (figuratively) Something that serves to reveal something else.

   The telltale was the lipstick on his shirt collar.

   • Saintsbury

     It supplies many useful links and telltales.

4. (music) A movable piece of ivory, lead, or other material, connected to the bellows of an organ, whose position indicates when the wind is exhausted.
5. (nautical) A length of yarn or ribbon attached to a sail or shroud etc to indicate the direction of the flow of the air relative to the boat.
6. (nautical) A mechanical attachment to the steering wheel, which, in the absence of a tiller, shows the position of the helm.
7. (nautical) A compass in the cabin of a vessel, usually placed where the captain can see it at all hours, and thus inform himself of the vessel's course.
8. (engineering) A machine or contrivance for indicating or recording something, particularly for keeping a check upon employees (factory hands, watchmen, drivers, etc.) by revealing to their employers what they have done or omitted.
9. (ornithology) A bird, the tattler.

• tell tales

telltale (comparative more telltale, superlative most telltale)

1. Revealing something, especially something not intended to be known.

   His eye was blinking, a telltale signal that he was lying.

   He blushed when he approached, a telltale sign that he was happy to see him.

• telltale compass