also: はんぱもん
noun
A derogatory term for a person who is incompetent, unreliable, or lacking in ability; literally 'half-baked person'. Used in casual, often insulting contexts.
あいつは半端者だから、大事な仕事は任せられない。
He's a halfwit, so I can't trust him with important work.
そんな半端者と一緒に働
I don't want to work with such a blockhead.
Compound of 半端 (はんぱ, 'half-finished, incomplete') and 者 (もの, 'person'). The reading はんぱもん is a colloquial contraction.