From Longman Dictionary of Contemporary Englishflatlyflat‧ly /ˈflætli/ adverb 1 → flatly refuse/deny/oppose etc something2 EMOTIONALwithout showing any emotion ‘Aunt Alicia has changed her will, ’ she said flatly.
Examples from the Corpus
flatly• It is also true that the two main Opposition parties have energy policies which are flatly contradicted by their environmental policies.• He had spoken very flatly, making his introduction sound like a threat.• He said flatly that there was no chance of a reconciliation.• When she had first proposed doing the piece, her bosses had flatly turned down her proposal. 