When, while part of a large group of other males, one male exposes his shaved scrotum to another member of the group, usually in a surprise manner.
Hey Chuck, look at this... ( exposed scrotum )...!
Chuck, "No way, I've been bald mikey'd!"....
When you shave your head so you have a "U" shape hairline and then rub the bald spot on a women's muff.
My girlfriend likes it when I give her the bald mikey.