Someone who is extremely careless, stupid and a hazard to be around. Trips over shoes constantly, breaks anything he touches, should not be alowed around heavy machinery or anything that might put other's lives in danger.
Mr Clutz walks into old, rich woman's house with lots of v. elaborate, precariously placed ornaments and brakeables scattered around.
Clutz: Oooh look a penny!
(As he picks up penny, knocks down v. expensive china vase)
Old woman: Good heavens! That vase was my Great Grandmama's!
Clutz: Huh? What vase?
When one is pretending to be knowledgeable of a subject that they know nothing about.
Knolegable person: Daft Punk's new song is just soooo lame. Don't you think
Crompastomper: Oh...erm...sure...I uh think that also. Cough...cough.
Knwledgable person to other knwledgeable friend: Oh he was soooooooo crompastompin'!