From Longman Dictionary of Contemporary Englisha kick up the arse/backside/pants etca kick up the arse/backside/pants etcinformalCRITICIZEPUNISH criticism or strong encouragement to make someone do something they should have done What Phil needs is a good kick up the arse. → kick
Examples from the Corpus
a kick up the arse/backside/pants etc• They like to see officialdom and the upper classes getting a kick up the backside.• I think I just needed a kick up the backside.• He was gormless, spoke in a funny nasal accent and looked as if he could do with a kick up the backside. 