It can mean precisely as it sounds, one who has sex mothers, but it was originally meant as "one who has sex with their own mother".
It is most of the time used without meaning, just to be said in a sentence, it can mean absolutely nothing and absolutely everything its meant to at the same time.
Also is used constantly to denote someone is a moron, a trife, a back stabber, and any number of other completely unrelated meanings.
"What the motherfuck is going on here?"
"Motherfucker, motherfucker, motherfucker...!"
2. Your party sux. This moter fucker is boring.
3. Im hungry as a mother fucker.
4. When i hit you, that mother fucker is gonna hurt.
5. Im broke like a mother fucker.
you are one bad mother fucker (compliment)
man, i'm high as a muther fucker (??)
look at this mother fucker right here. (??)
Motherfucker has taken on additional meanings through continued use, its evolution being shaped primarily by, again, the African-American community. It has come to mean a formidable or inexorable force, as in the threat: "Payback is a bitch, but revenge is a muthafucka." It is also an expression of disgust or contempt: "Now, ain't that a muthafucka!" Motherfucker also has come to be used in some circles as a general pronoun.
The initials M.F. became a common, more polite substitute for motherfucker, as did the term Maryland farmer in the 1960s and 1970s. The result is an oft-recounted, if somewhat apocryphal, tale of the clueless Maryland Farmers Association writing a letter of protest to a prominent African-American in the news. It seems he called a Capitol Hill politician a "jive Maryland farmer," and the association's members were mightily offended.
The growing use of motherfucker in American popular culture may mean the term through time has become less offensive to some, but some see its increasing ubiquity as a sign of the general coarsening of American society.
Still, in a way, a father, stepfather, or stepmother is a motherfucker; who else would be fucking one's mother?
Father: "I'm your father! Don't talk to me like that!"
Son: "I meant literally. How else do you think I got here?"