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).
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?
Its when you stab a lava lamp up a girls somewhere near the balls
You are motherfucker you bitch
Your mother fucker killed you
Any asshole who you don't want fucking any of your female relatives, such as you mother, sister, brother, pets, steps, uncle, aunt, cousins, nephew, niece, friends, the local barber, the gas station attendant, your investment banker, the ATM at your bank, etc. etc.
My cousin Boo Boo from North Dakota told me that she was so upset that after her father "boinked" her mom, he came after her, and then she went after him with a baseball bat. "What a mother fucker!" she said, and something else I can't say.
Any asshole you don't want fucking your female relatives, e.g. your mother, sister, aunt, niece, cousin, grandma, pets, steps, brother, nephew, uncle, grandpa, best friend, any friend, possibly your enemy, the gas station attendant, the milkman, your doctor, the barber, the bar tender, your investment banker, the ATM outside your bank, the ATM inside the Walmart. the AI inside the Target, the local cops... oh, wait, the cops don't belong on this list.
My cousin Honey Boo Boo told me that her dad first boinked her mom then came after her. "What a mother fucker!" she said, as she came at him with a baseball bat. I love my cousin Honey Boo Boo.
Somebody you don't want fucking any of your female relatives, including your mother, sister, aunt, niece, steps, brother, cousin, nephew, friend, pets, uncle, etc, etc., etc.
My father is a real mother fucker. After fucking my mother, which was bad enough, he wanted to fuck me. Gross!
Guy 1: You are a mother fucker!
Guy 2: Your mother says so too!