(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.