'Gregging' is the process by which an individual masturbates into a hat. Though this is its definition, it can also be used to describe an individual resting his penis in a hat, and/ or using the hat to masturbate. To 'Greg' someone is to steal their headwear, and perform one of these heinous acts using it.
Example 1)
It has commonly been used to make amusing adjustments to songs:
"Gregging,Gregging you... filling up your beret with my penis"
Example 2)
Ray: "Man, what the fuck is up with your hat?"
James: "you wont believe it, Some punk gregged it last night at the party!"
Ray: "Ouch, dont worry about it, weve all been there before"
Example 3)
Mark: "Hey, look at that blokes hat, you want to greg it?"
Bryn: "Hell yeah!, ill go first"
30 minutes later
Man with Hat: "Bollocks"
(V.) To Old Gregg on someone is to hit on someone very creepily and awkwardly, usually in an attempt to get that person to do something he or she doesn't want to do but that you do.
Effective examples of old gregging include:
1. throwing out continuous strains of awkward, senseless questions, such as: "do you want to go to a club where people wee on each other?" or "do you ever drink baileys from a shoe?"