A person who is doing anything that may be related to jinxing you while also behaving like a fuck. Normally this term is reserved for more serious jinxing implications such as pregnancy or suffering consequences one was hoping to avoid.
friend.." hey wouldn't that suck if you got that skanky girl pregnant?"
you" what the hell is wrong with you you jinxfuck?!"
Jinxing yourself on getting fucked. Killing your chances of "gettin' it". Cockblocking yourself.
Quit trying to grow your beard out, your jinxfucking yourself with the honeys!