a secret warning or piece of information, especially one given to the police about illegal activities:
The arrests came after a tip-off from a member of the public.
2 American English informal
something that shows you that something is true, even though you did not expect it to be true:
The fact that he hasn't called should be a tip-off that he's not interested.
the beginning of a basketball game, when the ball is thrown into the air and two players jump up to try to gain control of it