The mother of any one or more than one friend that is incredibly hot. The difference between a "milf" and a Scott's Milf" is that the latter has an inclination to release sexual tension on the friends belonging to her firstborn son.
A term used for attractive older women if you're not sure if they're mothers or not (used when you're unsure if a person is a real MILF)
A: "Woah! Mrs.Jones is so hot,she's a total MILF"
B: "we're not sure if she has a kid so does she count as a MILF?"
A: "Well she's a Schrodinger's MILF,there's a chance she's a mom but there's also a chance she's not a mom at all!"
B: "you're making it complicated"