noun
hidden talent; party piece; parlor trick
A skill or performance one can do but doesn't usually show; often a surprising or amusing trick revealed at social gatherings.
彼の裏芸は、一発芸でみんなを笑わせることだ。
His hidden talent is making everyone laugh with a quick party trick.
宴会で裏芸を披露した。
I performed my party piece at the banquet.