BILF is BOSS I'd Like to Fuck.
The whole point of having the acronym (like MILF) is that it's a bit taboo.

boy i'd like to fuck

Acronym: Brother I'd like to fuck.
N. Term applied to hot (usually older) brothers of best friends (bfs) or aquaintences. Used when around said targets sibling or other friends who know of siblingship.
Akin and sometimes used in place of the rarer Filf (Family I'd like to fuck; i/e:cousin, step siblings ect., aunts, uncles, cousins inlaw - of friends)
Derivitive of Milf
Note: does not denote an incestual connotation.

Beer Induced Leg Failure. A condition where by the sufferer falls over and hurts themselves or looks stupid. Condition is caused by endulging too much in the glorious amber ale we know as beer. Symptoms which indicate a case of BILF is iminent include swaying and stumbling.

Brother I'd Like to Fuck.

bitch I'd like to fuck

Beard I'd Like To Fuck.

Glorious beards on glorious men.