slang An especially important, influential, and authoritative person, especially someone who is overbearingly or arrogantly so. We're just waiting for the muckety muck to give us the green light before we get the project started.

slang An especially important, influential, and authoritative person, especially someone who is overbearingly or arrogantly so. We're just waiting for the muckety-muck to give us the green light before we get the project started. "All hail the muckety-muck," Jerry muttered under his breath as the dictator's motorcade rolled by.