A distant cousin of the BigMac Attack, a Gigaschnack Attack is the inexorable urge to purchase and consume massive quantities of low quality highly processed vending machine food.
Abbr. GSA
Person 1"Hey are going to get dinner tonight?"
Person 2"Naw, I'll probably just have a gigaschnack attack later"
Person 1, "I say, you haven't eaten all day, you must be starving!"
Person 2"Naw that aint me, I had a 5000 calorie GSA earlier"