Similar to a Cincinnati Bowtie, a turkey helmet is the act of sitting on a face, with your nutsack and dang on the other party's neck. Preferably, your asshole will be atop the point of the victim's nose. In this position, your scrote resting on the neck will look like a turkey's fleshy neck.
After that fucker that disrespected me at my own party passed out, I pulled down my pants and gave that dicksucker a serious Turkey Helmet. Talk about hilarity!