A tip-off is a piece of information or a warning that you give to someone, often privately or secretly. The man was arrested at his home after a tip-off to police from a member of the public
An anonymous caller tipped off the police that the suspect would be in the area.
If someone tips you off, they give you information about something that has happened or is going to happen. Greg tipped police off on his car phone about a suspect drunk driver He was arrested two days later after a friend tipped off the FBI
give insider information or advise to; "He tipped off the police about the terrorist plot"
give insider information or advise to; "He tipped off the police about the terrorist plot