To have a mouth that seems like a potty either symbolically or physically to others. It is believed to first be encountered mysteriously during an online chat with Finn the goldfish. Many debate as to whether this incident ever happened.
Hey, could you open that pottymouth of yours? I need to go.
An act of love (or hate) between two homosexual lovers where each person takes turns farting into each others mouth, inhales the gas, kisses and then proceeds to burp while still making out.