A person who loves to get a fat load or a wad or straight up cum (gism) all over their dome.
They usually grab the cock and smack their face with it while it's expelling the gizz. If the gism face is a guy, he will just rub his face inside the pussy like no tomorrow.
You can usually spot a gism face because they usually have a little gizz on their face.
Reference the movie 'Bruno" where meets the ghost of Milli Vanilli, if that scene was real, Bruno would obviously be the gism face.
Dude, that chick must love the cock, she's got a major gism face.
Hey, you've got some sour cream on your cheek, wipe it off before someone mistakes you for a mega gism face.