An nice, plump backside that's ripe for spanking or anal penetration. Most clearly defined as an ass big enough to hold a cocktail or libation similar to a shelf ass.
Jane has a great Willum Ass, I know this because an ass becomes good when I can rest my beer on her ass when she's standing up.
Someone so incredibly cool, that I had to google synonyms for awesome to simply try to contaminate even a fraction of how amazing, astonishing, awe-inspiring, breathtaking, imposing, inspiring, magnificent, majestic, miraculous, spectacular, staggering, stunning, stupefying, sublime, wonderful, wondrous, epic, legendary, cool, neat, keen, sensational and excellent you are if you are Willum.