That is merely a phonetic spelling of the word "asshole", as pronounced by Japanese actors (or actresses) in more recent monster-destroys-Tokyo flicks or martial arts movies. (Japanese are becoming less polite in the movies than they used to be, in an attempt to reach the modern teen audience.)
Example: Eager Japanese photographer in high rise building snaps close-up of Godzilla using flash! Godzilla is irritated by the flash and turns his head toward the balcony, opening his massive jaws and utterly an ear-piercing screech that breaks about a hundred windows, and strips off the cameraman's glasses and tie.
Cameraman's smarter buddy (the hero) snaps, "ASTHORE!!! Now rook at what you've done!"
Cameraman and hero run frantically for elevator, as Godzilla ponderously begins to get his radioactive flaming breath into gear....nice slow motion shot of flaming breath taking out huge chunk of high rise...
Hero and cameraman scramble out of half-demolished and smoking elevator in the basement. Hero's girlfriend (spunky Japanese journalist/science-lab assistant) rushes over and cries "What happened, Jiro?"
Hero says, "Ask the asthore!" Cameraman grins sheepishly and shrugs.