This has 2 meanings:
1. Literally it means someone who has sex with his own mother, but this word is hardly used in this context(Just like when you call someone a bastard, you don't mean he is a bastard child, when you call someone a mother fucker, you are usually you are not implying that he is someone who sleeps with his mother).
2. The mother of all fuckers(this is what people actually mean when they call someone a mother fucker).
1. Literally it means someone who has sex with his own mother, but this word is hardly used in this context(Just like when you call someone a bastard, you don't mean he is a bastard child, when you call someone a mother fucker, you are usually you are not implying that he is someone who sleeps with his mother).
2. The mother of all fuckers(this is what people actually mean when they call someone a mother fucker).
definition 1:
Tom: Go fuck your mother...
Jerry: Only a mother fucker(the context of this word is literally someone who has sex with his own mother) like you will do such things.
definition 2:
50 cents: Yo mother fucker! wassup!
Eminem: yo fiddy...nothing much...hows it going?
Tom: Go fuck your mother...
Jerry: Only a mother fucker(the context of this word is literally someone who has sex with his own mother) like you will do such things.
definition 2:
50 cents: Yo mother fucker! wassup!
Eminem: yo fiddy...nothing much...hows it going?
by kundinella@1 January 30, 2018
Get the mother fuckermug. “ the mother fucker is incest”
by RapaTuMadreLLC September 13, 2021
Get the The Mother Fuckermug. those little shitheads from down the street that you just want to stop singing so bad that you curb stomp them away
by the doo wop bandit June 26, 2015
Get the doo wop looking mother fuckermug. by DR.WAKENSTEIN November 29, 2019
Get the Mother fuckermug. "Man my feet are ugly" while talking in the presence of someone with ugly feet in response the other party would say "man your a Sideways mother fucker"
by Coloradonik April 20, 2024
Get the Sideways mother fuckermug. 
Just don't fuck with the dü. He one crazy ass mother fucker. Oh ya and get a new dictionary mõth3r fûckēr
by CANB-GFMF November 28, 2022
Get the Crazy ass mother fuckermug.