half-arsed /ˌhɑːf ˈɑːst◂ $ ˈhæf ɑːrst/ BrE AmE British English , half-assed /ˌhɑːf ˈæst $ ˈhæf æst/ American English adjective [only before noun] informal
1 . doing something without making much effort:
He made a half-arsed attempt to clean up after the party.
2 . completely stupid:
What a half-assed idea!