Acronym, short for: Number One Mother Fucker What's In Charge.
Originally a Naval term similar in usage to REMF, NOMFWIC is much more obscure. The NOMFWIC is one who is in charge and makes sure no one forgets it, even when he or she is dead wrong.
Ensign 1: "Shut up, NOMFWIC on deck!"
Ensign 2: "Crap, my uniform is untucked."