shitless

From shit +‎ -less.

shitless (not comparable)

1. (vulgar) Having an empty bowel; greatly frightened; see usage notes below.

   He was scared shitless.

• This term is primarily found in the verb phrase scare shitless (“to frighten (a person) to the point that he vacates his bowels”) and its participial adjective scared shitless (“frightened to the point that one has vacated one's bowels”). It may be considered a more evocative variant of certain uses of witless and speechless.

• spitless (euphemism)
• witless