Meaning

noun an actor's line that immediately precedes and serves as a reminder for some action or speech

noun evidence that helps to solve a problem

noun a stimulus that provides information about what to do

originFrom Middle English cu (used for half a farthing, from q as an abbreviation for Latin quadrāns (“quarter of an as”)), from Latin cū, kū. Compare French ku.

Etymology from Wiktionary, CC BY-SA 3.0