Rappers that make music with lyrics very difficult to understand or rappers that make a song with very basic lyrics and use adlibs(ay,yuh) to make it sound dope.
An example of Mumble Rap:

Bitch im hella rich, ay
Fucking on yo bitch, ay
Made her suck my dick, ay
Nutted on her lip, ay
by Shux_ June 21, 2017
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First of all, contrary to what mumble rappers and hardcore fans of mumble rappers would like you to believe, mumble rap is real. And in most cases, it's simply not okay. You know you are listening to Mumble rap if you run into the following:

1. You cannot understand what the fuck they are saying.
2. You can to some degree but are still concerned about their intelligence and/or speech capabilities.
3. You cannot understand what the fuck they are saying.
4. It's impossible to sing along short of humming or speaking complete gibberish yourself.
5. You cannot understand what the fuck they are saying.

When the 5 main tell-tell signs above are stressed, they are not referring to a couple of words you may have had trouble hearing correctly and mistake for something else. You cannot, and I mean CANNOT understand the entirety of the song WITHOUT looking up the lyrics. You always have to look up the lyrics of any song, but with most NORMAL songs, you have guesses of what is actually said in full. With Mumble Rap, you have ABSOLUTELY, NO FUCKING IDEA, AT ALL, of what is actually said. Even if you have special linguist powers and do guess some of the words, you'll most likely be surprised to find out there are 4 or 5 words in the hook that you did not even pick up on, let alone make sense out of. And you'll likely find even more during verses. In fact, the chances of you having a clue of what is said at all during a verse are very very very low. That's how bad Mumble Rap is.
Examples of Mumble Rappers include: Young Thug(Worst case of this motherfucker is the song "Lifestyle"), Desiigner(Goddammit, he is the epitome example of everything written above), Future(To a lesser, but still concerning degree than the two aforementioned)

Other rappers who are not as bad as the three above(Usually, that is) but still have their fair share of problems include: Lil Yachty, Lil Uzi Vert, and Quavo from Migos(And many many more)
by chickewingzbruh August 3, 2017
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A style of rap that originated in the South and spread to other places like Chicago and the New York/New Jersey area. The style usually consists of "mumbling" rap lyrics and sacrificing pronunciation clarity.

The mumble style likely is influenced from the following elements: the Southern drawl & pronunciation, the drinking of the drug "lean" which can slur speech patterns, and the wearing of gold teeth which affects pronunciation.

Example of Mumble rappers are: Future, Desiigner, Chief Keef, Migos, Gucci Mane, Fetty Wap, Young Thug, Lil Yachty, Lil Uzi Vert, and Rich Homie Quan
Example of a Mumble Rap verse:

"Ah juh tooh suh molluh what es?
Gah suh bih from Follie wit us
She wanna fuh da squa, what es?
I'ma fuh huh braws, what es?
Bih fruh Pah'stan what up?
Ferraris and them Lambs, what es?
Bou ta fuh dis cluh up, what es?"

- Future, 2016
by TheoHux January 6, 2017
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Rapping while sucking a dick. It was formed when a man bet his friend that he could out rap him while sucking a dick and the friend didn't want to get out rapped by someone sucking a dick so he also began to suck a dick and rap at the same time.
"Aye!!! wtf??? Is Daquan sucking a dick over there? Why he moaning so fucking loud?"
"Nah man, he just performing a mumble rap, its straight brah."
by a326159487124357689 February 14, 2017
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When "Rappers" mumble incoherent absolute garbage for an entire album/track, destroying Rap as a genre and disgracing black people as a whole.
Fetty Wap, Young Thug, Chief Keef, Rich Homie Quan, Future, and Desiigner are mumble rapping pieces of garbage.
by Rastaguy2 September 10, 2016
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A Rap song sung in very low tone or with no character (robot voice) or can barely be understood
Dude Lil Pump Makes Mumble Rap
by Harvard_Dropout August 9, 2018
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'Mumble Rap' Term Used For Rappers With No Sign Of Authenticity In Their Rap Usually Seen As Artists That Bootleg, Sell Outs, And Errant Viral Rappers With Rap That Can Come Out As Unclear.
One Of Those Viral Hits This Year Was Blatantly A Trash Mumble Rap.
by Mix-Race Man On Road September 15, 2018
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