Simply a variation on the classic MILF that is well known. This is referring to a "Mother-In-Law-I'd-Like-to-Fuck."
That dress your mother-in-law was wearing at the wedding seriously made her look like a MILILF.
by Dr.Gutin February 21, 2006
Mother-in-law I'd like to fuck - a theoretical possibility but never reported in the masturbatory literature.
I married her because her mom was hot, a real MILILF
by Alybrella January 12, 2011