flatter vs brown-nose

flatter and brown-nose both are verbs.

Word	Noun	Adjective	Verb	Adverb
flatter	No	No	Yes	No
brown-nose	No	No	Yes	No

As verbs, brown-nose is a hyponym of flatter; that is, brown-nose is a word with a more specific, narrower meaning than flatter:

Other hyponyms of flatter include soft-soap, adulate, stroke, bootlick, fawn, kotow, kowtow, suck up, toady, truckle, butter up.

flatter (verb)	brown-nose (verb)
praise somewhat dishonestly	flatter with the intention of getting something