A mudder is redneck slang for a 4X4 car, truck, or ATV that has been lifted, and fitted with huge tires for the purpose of driving through mud pits. It's a pity that mudding has a hick stigma attached to it, as it's hella fun. Something about the combination of beer, ugly rigs, and a huge mud pit just hits the macho spot.

A person who attends Harvey Mudd College in Claremont, California.

A mudder -- also known as a muddie or mudhead -- is a person who spends a great deal of time playing the online games known as MUDs. Only a few years ago, mudders were a common sight in college computer labs, alongside IRCies and, occasionally, gweeps. Today, though, most recreational Internet users wouldn't know a MUD from a spud; while many MUDs survive, more "user-friendly" online games have largely eclipsed them in popularity.