Available Definitions:
1) superl. - Offensively filthy; very dirty, foul, or defiled; disgusting; nauseous.
2) superl. - Hence, loosely: Offensive; disagreeable; unpropitious; wet; drizzling; as, a nasty rain, day, sky.
3) superl. - Characterized by obcenity; indecent; indelicate; gross; filthy.