A very insulting term used to piss someone off. This doesn't neccesarily mean your mom has a penis, but the thought of it, would piss someone off. It's a good way to get someone to shut the fuck up when they talk a lot or when they ask a stupid question.
*Guy 1: Yeah, so can you believe that Julie is telling all her friend's I still like her?..the nerve of that bitch....
Guy 2: Yeah, well I heard your Mom's penis is the talk of the town.
*Guy 1: "Hey, I wanna drink tonight, so maybe you can drive".
Guy 2: "Maybe your Mom's penis can".
An insult your mom has a penis therefore your mom is gay with your dads penis.
Guess what i saw yesterday. Your moms penis. Gross my moms not a guy. your moms penis tells me a different story.