bluffly vs flat out

bluffly and flat out both are adverbs.

Word	Noun	Adjective	Verb	Adverb
bluffly	No	No	No	Yes
flat out	No	No	No	Yes

As adverbs, bluffly and flat out are synonyms defined as:

Other synonyms of bluffly include bluntly, brusquely, roundly.

bluffly (adverb)	flat out (adverb)
in a blunt direct manner	in a blunt direct manner
	at top speed