adverb, adverb taking the 'to' particle, noun or participle which takes 'suru'
clearly; plainly; decisively; flatly
Mimetic adverb describing a firm, unambiguous manner of speaking, refusing, or deciding. Often used with 言う, 断る, or 決める. Can take と or する.
彼はその申し出をきっぱり断った。
He flatly refused the offer.
To put it plainly, that's a mistake.
彼女は自分の意見をきっぱり述べた。
She stated her opinion clearly and decisively.