Motherfucking is not a word for a person. That person-word is motherfucker. This one is a very rude adjective and adverb, made later from motherfucker. People stick it in front of a noun to show fury, or to make the thing feel cursed: the motherfucking printer, my motherfucking keys. It works like a much dirtier damn or bloody. You can also use it as an adverb: I am motherfucking tired. Do not use it. Though actually, you will hear it in films, songs, and angry talk, and it often no longer carries the old incest insult — it just means “I am extremely angry” or “I mean this very strongly.” That does not make it polite. For a student, it is never safe.