bounce off (of something)
to rebound from something. (Of is usually retained before pronouns.) The ball bounced off the wall and struck a lamp. It hit the wall and bounced off.
bounce something off (of) someone or something
1. Lit. 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. She bounced the ball off of Harry, into the wastebasket.
2. and bounce something off Fig. 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?