A boobstand is generally defined as the female lies on top of the male, while he is holding the female's shoulders with his hands, and he tittyfucks the female.
Mike: Dude, I totally gave this chick a boobstand last night. It was quite enjoyable.
A girl who has big breasts and uses them lies them onto of a short male friend or kid due to stiff shoulders Cases like these would probably be in anime....
Boy- "MOVE YOUR BREASTS YOU OLD HAG I'M NOT YOUR BOOBSTAND"
Girl- "Old Hag I'm not even 20 now stay still brat