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wheel: n.

[from slang ‘big wheel’ for a powerful person] A person who has an active wheel bit. “We need to find a wheel to unwedge the hung tape drives.” (See wedged, sense 1.) The traditional name of security group zero in BSD (to which the major system-internal users like root belong) is ‘wheel’. Some vendors have expanded on this usage, modifying Unix so that only members of group ‘wheel’ can go root.