A six pack that one has because they have absolutely no body fat that would conceal a lack of muscle.
Girl: Wow, that guy's got some great abs! Look at that six pack. Do you work out?
Guy: Nope, these are default abs, baby.
When a dude has abs because he's so skinny.
Omg Katie, did you see Tristan's abs?
Girl he's like 100 lbs...those are default abs.