noun A small portion of bread or beer; the quantity bought with a farthing or half farthing and noted with a q (for Latin quadrāns (“farthing”)) in the buttery books.
noun An action or event that is a signal for somebody to do something.
noun The last words of a play actor's speech, serving as an intimation for the next actor to speak; any word or words which serve to remind an actor to speak or to do something; a catchword.
noun A marker or signal that triggers something, such as the start of an audio recording.