'goofball' definitions:

Definition of 'goofball'

(from WordNet)
noun
A man who is a stupid incompetent fool [syn: fathead, goof, goofball, bozo, jackass, goose, cuckoo, twat, zany]
noun
A person who amuses others by ridiculous behavior [syn: clown, buffoon, goof, goofball, merry andrew]