When a guy is receiving head, he unstraps his belt so that as the girl goes in to deepthroat, he can use the belt to lock her in place. This can continue until she sees stars and passes out.
Dude, this girl was going down on me and I totally went all Orion's Belt on her to get the most out of it!
When a girl has 1 nipple ring, a bellybutton ring and a clit ring, it is known as an Orion's belt, because it is in a line similarly to the three stars in the constellation Orion.
Dude 1-"Dude i was hooking up with this chick last night and she had the trifecta, nipple ring, a belly button and a clit ring."
Dude 2-"Oh she had Orion's belt going on there."