An adverb meaning to act decisively or say something plainly and firmly; to do something without hesitation or ambiguity.
彼女はプロポーズをきっぱり断った。
She flatly refused the proposal.
きっぱり言うと、彼はもう来ないと言った。
To put it plainly, he said he wouldn't come anymore.
今後その仕事はきっぱりやめるつもりだ。
I intend to quit that job decisively from now on.