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?