Purposeful nippling is going after the nipples with a purpose like are you gonna bite them? You want to lick them? Or can I just get a nibble. Simply put, it’s going at the nipples with a purpose. As opposed to accidental nippling where somebody’s nipples end up in your face and you’re overwhelmed by the nipple and compelled to put it in your mouth and do something with it. See accidental nippling for this.
When a bloke has half a hard on and sits down to take a piss. He adjusts on the seat to stop getting piss all over the place and his nob slips under the rim of the seat, thus when he sits back down he squashes his nob between the seat and the rim.
Nob nipping - usually happens in the morning after a hard night on the piss, or after a shag or to blokes that are well endowed. May in fact be the only down side to having a huge penis.