Meaning
To secretly warn someone or give them inside information.
Example Sentence
"Someone tipped off the police about the robbery."
Synonyms
warn
inform secretly
notify
Usage Note
This phrasal verb is separable. When using a noun object, it can go between the verb and particle or after the particle. When using a pronoun object, it must go between the verb and particle (e.g., "turn it off" not "turn off it").