Typically the word you say for "Fuck me!" In a matter of sexual acts or some shit.
Another definition is "Fuck" for when you failed some shit, or fucked up something bad. Smh. For example,
"Fuck me daddy!"
"Fuck, I failed on the shit again."
It means something alike to, "Fucked you over".
"Trust me, have I ever steered you wrong before?" - Jack Vincent (BO3)