A clueball is a person who does dumb things either frequently or infrequently. It can also be used to describe someone who makes stupid comments or is really weird or eccentric. Clueball is also used to describe bad drivers. Clueball can be used as a noun, verb, or adjective.
Gerry is an absolute clueball.
That person is driving like a clueball.
Hey look at that clueball over there.