Kick-ass and Kiss (someone's) ass are nasty street language Kick-ass An offensive term meaning forceful, aggressive, or ruthless Kiss (someone's) ass Do something that most people wouldn't in order to get something in return.

Also, if you hyphenate it (kick-ass), it becomes an adjetive. It means "impressive" or "spectacular" or "exceptionally good". Example: You did a kick-ass job on your exam. She is driving a kick-ass car.

Kick ass - 1) you really kicked (hit someone with your foot) on their ass (bottom/behind/bum). 2) you did something really well and probably did better than everyone else or better than everyone was expecting "Well done! You really kicked ass in that assignment!" Kiss ass/kiss somebody's ass - be nice to them in order to get something in return. It is the verb that is associated with the nouns "brown-noser" or "suck-up". "You must have kissed the teacher's ass to get that grade" "Whose ass did you have to kiss to get that new car?" Kiss ass looks weird written down - I think it's one of those things we just informally say as slang. Be careful when you use it and who you use it with!