big wig
1. A prominent or significant person. That guy's a real big wig in the art world, so please don't say anything to embarrass me.
2. Someone who is arrogant or conceited. Quit acting like such a big wig—you're no more important than the rest of us.
bigwig
n. an important person; a self-important person. Some bigwig in a pinstripe suit waltzed through and asked me to leave.