The act of sliding one's penis between the ass cheeks of another; sliding the "hot dog" between the "buns".
"Wendy giggled as she gave her male friend Mike an assjob". Many people in today's society do not classify assjobs as sexual activity; they are more like massages, and thus can be shared between friends.
When a girl lubes up a guyscock and gently grinds her ass cheeks on and gets him off. That or he lays his cock between her ass cheeks and strokes away without penetration.
Stacy has such a soft sexy ass. I love it when she lets me lube it up and lay my cock between those cheeks and grind on it for a great ass job.