conjunction, particle
and yet; even though; in spite of
Conjunction/particle expressing contrast or dissatisfaction, similar to くせに but slightly more emphatic or colloquial. Often used to criticize or express surprise at someone's behavior given their circumstances.
See also: くせに
彼は何も知らないくせして、偉そうに話す。
He talks arrogantly even though he knows nothing.
あの子、まだ子供のくせして、大人みたいな口をきく。
That kid talks like an adult even though he's still a child.