Hot mom means sexy mom; deduce that to mean mom I'd like to have sex with;
regard that statement as
Mother I'd Like to Fuck, hence the terminology: MILF.
Joey:
Wow, Ross, your ex-wife Carol is one hot mom.
Ross: You're talking about my son's
mother.
Joey: Hey, I call 'em as a I see 'em. I'm sure Susan
will agree that she's a MILF.
Ross: Shut up!