What does the idiom “Kick Ass, Kick Butt” mean?
Definition:
1) Defeat badly; 2) be excellent or highly effective (only “kick ass” would be used for 2)
For example:
“1) Madrid won most of our matches during the season, but we kicked ass in the playoffs. 2) That movie kicked butt! It was so exciting.”
Notes:
To “kick someone’s ass” is slightly different, meaning to physically beat someone badly in a fight. Definition 2) may also be used as an adjective, “kick-ass”: That car has a kick-ass engine. Both “kick ass” and “kick butt” are somewhat crude; “kick ass” is more so.