Usually referring to a female but could also apply to a male. Can be used as both a noun describing someone's butt or as a nickname. Refers to someone with a large butt that sways while walking due to their natural swag.
Note: this is not a large butt due to the person being heavy, it is a naturally lush ass, sometimes associated with black girls
Nate: "Look at that girl, she has a swaggabooty."
Kevin: "Oh hey, swaggabooty."