It's that thing that only a borderline cocky/confident guy presents that girls should watch out for, but will surely allure them in to boning a guy that is no good for them. May be present in forms of sarcasm, smirks or a guy that is good looking and knows it and uses it to his advantage.
Guys with no jobs or just plain out losers that try to hard to get girls do not have this, those are just douche bags, period.
Girl: I totally want to bone my neighbor.
Friend: Yup, he has that douchy swag!
An anatomical abnormality where a female, when taking off her underwear, reveals a large labia majora or flap which 'unrolls' when the underpants are removed. Similar to unrolling a camping swag.
Craig: I think its time you took off your underpants.
Stripper: OK, but I need to warn you, I have a swag.