A continuation of the shoulders over the elbows. Similar to "cankles," but on the arm.
This phenomenon occurs when the fatty portion of the shoulder is too much to contain to the upper arm alone, thus it overlaps the elbow and continues on the forearm. It is possible for this to continue all the way to the hand, as with 'cankles.'
"Her shelbows looked like the end of a hot dog sticking out of the bun."
When an extremely obese person's shoulder fat appears to travel south and engulf the person's elbow. Combination of "shoulder" and "elbows".
Brett: Yo, check out that dude in line at Baskin Robbins.
Gabe: Geez, looks like he doesn't need any more ice cream cause he's rocking some crazy shelbows.