slang An especially important, influential, and authoritative person, especially someone who is overbearingly or arrogantly so. (Sometimes shortened to simply "muckamuck.") "All hail the high muckamuck," Jerry muttered under his breath as the dictator's motorcade rolled by. We're just waiting for the muckamuck to give us the green light before we get the project started.
(lord) high muck-a-muck
Rur. a very important person. (Humorous.) Jim's acting like he's some kind of lord high muck-a-muck. What's gotten into him? Mary got a promotion, so now she's a real high muck-a-muck.
See also: high