kick butt

bust one's butt

To work exceptionally hard.

butt heads

To argue uncompromisingly.

butt in

To join a conversation or situation in which one is not welcome or invited; to interject (connotes a rude or discourteous interruption).

butt up

To touch closely, to scrape (against); to press firmly (against).

full butt

headfirst with full force

get a kick out of

To be delighted by; to be amused by.

get one's butt somewhere

Go somewhere, especially quickly.

kick a dog when it's down

To make things worse for someone in an adverse situation.