Extremely disgusting, or filthy; excessively nasty; nasty(X10).
"Dude, did you have to blow up my bathroom? It smells MAGNASTY in there."

"Hey look at that chic. Does she have armpit hair? . . . damn, that's MAGNASTY."

"Why the hell do you have beastiality porn on your computer!!! You're fucking MAGNASTY."
by A. Boss March 13, 2008
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