What's a spline? = W = wheel bit

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.

--The Jargon File version 4.3.1, ed. ESR, autonoded by rescdsk.