After a weekend of drinking beer, eating all those chilli dogs, poutine, and whatever else came in contact with your lips, shitzilla is what attacks you (usually on sunday evening) when you tremble as you approach the toilet.
"Oh man, Shitzilla's on the prowl, can you hear him growling?"
"*Whew* Shitzilla really took a round out of me that time"
In most cases refering to the female to be a massive slut and or cunt. Signs of a skagzilla include but are not limited to being a bitch, multiple STD's, C-section scars from those always fantasic one night stands, has given or gotten a clevland steamer, or if you are "that guy/girl"
Dude1- So that hot chick Jesica turned out to be a massive skagzilla
Dude2- Might want to get your self checked
A dirty whore that likes to have intercourse with several men at the same time. she also has messed up teeth. Derived from the video game Boarderlands.