Fuck

An acronym with no formal etymology:

F.U.C.K

"Formal Use (of) Carnal Knowledge"

----->Carnal; Adj: the flesh in terms of sex

Has been bastardized to many other definitions:
n.) in reference to a person causing frustration

v.) in reference to fornication
v.)in reference to ruining something beyond repair
adj.) used to emphesize what is being described

F.U.B.A.R = "Fucked Up Beyond All Recognition"

(n.) "You dumb fuck!"
(v.) "It fucked everything up."
(adj.) "That's fucking stupid."