Noah Cyrus Blasts Troll with NSFW Comment After Family Love Triangle Joke

Noah Cyrus has broken her silence on the love triangle rumors swirling around her family ... telling a troll exactly what he should do with his mouth after he cracked a joke.

The singer-songwriter fired back at a hater on Instagram who brought up a rumor her mom, Tish, "stole" her new husband, Dominic Purcell, from Noah.

Noah -- using some of her trademark deadpan wit -- replied in the comments by asking the user to please "choke on the fattest c***" ... bit a of nuclear response, we gotta say.

Could be Noah's totally done with the online drama ... remember, reports surfaced several weeks ago claiming Noah was initially interested in Purcell before her mom swooped in and started bangin' the guy.

Word is, Noah's still pissed about it ... even skipping Tish and Dom's wedding last August -- and, she even wore a Billy Ray Cyrus t-shirt that day in what many saw as a not-so-subtle shot at her mom.

Of course, we published photos earlier this week of Miley and her mom walking around L.A. together ... seemingly proving the two are on good terms.

Miley reportedly confronted her mom about the alleged love triangle ... slamming the whole thing as downright strange, according to People. But it appears they've come to some type of understanding since then.