Used when someone is calling someone else (usually a friend) stupid this is usually as a joke just between friends but can sometimes be used in spite of someone else
Girl 1- haha your so stoopid
Girl 2- I know so are you lol
The actual level of ones stupidity determines how many O's are added to the root word STUPID.
Johnny's answer was more than dumb, it was down rightstupid, but the answer Jimmy gave was way worse,. Now we call Johnny Stoopid and Jimmy stoooooooopid