Blyxing is a self-harm "technique" in which the self-harmer pushes a sharp object (such as scissors, a knife, etc.) into their bellybutton. This usually induces a great pain in the user. While mostly unknown, some self-harmers prefer blyxing over cutting because no visible marks are left behind (though some are probably left inside the bellybutton) so a self-harmer could blyx unnoticed for an extremely long period of time.
Ryan: I heard you found out your girlfriend was blyxing, dude.
Matt: Yeah I walked in on her pushing a pair of scissors into her bellybutton, it almost made me cry.