drop a dime
Inform on or betray someone, as in No one can cheat in this class—someone's bound to drop a dime and tell the teacher. This expression, alluding to the ten-cent coin long used for making a telephone call, originated as underworld slang for phoning the police to inform on a criminal and occasionally is extended to any kind of betrayal. [1960s]
Words nearby drop a dime
droop nose,
droopy,
drop,
drop a bombshell,
drop a brick,
drop a dime,
drop a line,
drop arch,
drop away,
drop back,
drop bear