brusquely vs flat out

brusquely and flat out both are adverbs.

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

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

Other synonyms of brusquely include bluffly, bluntly, roundly.

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