Phrasal verbs, also called two-word verbs, are idiomatic expressions wherein the second element of the verb (the adverb or particle) is not necessarily predictable.
Phrasal Verb:
bounce something off (of) someone or something
Meaning / Example:
1. to make something rebound off someone or something. (Of is usually retained before pronouns.) > She bounced the ball off the wall, turned, and tossed it to Wally.
2. and bounce something off to try an idea or concept out on someone or a group. (Of is usually retained before pronouns.) > Let me bounce off this idea, if I may. > Can I bounce something off of you people, while you're here?
Phrasal verbs consists of a basic verb + another word or words. The two or three words that make up a phrasal verb form a short 'phrase' - which is why we call them 'phrasal verbs'.