Source : Webster's Revised Unabridged Dictionary (1913)

Monstrously \Mon"strous*ly\, adv.
   In a monstrous manner; unnaturally; extraordinarily; as,
   monstrously wicked. ``Who with his wife is monstrously in
   love.'' --Dryden.

Source : WordNet®

monstrously
     adv 1: in a hideous manner; "her face was hideously disfigured
            after the accident" [syn: {hideously}, {horridly}]
     2: in a terribly evil manner; "the child was heinously
        murdered" [syn: {heinously}]
     3: in a grotesque manner; "behind the house lay two nude
        figures grotesquely bald, with deliberate knife-slashes
        marking their bodies" [syn: {grotesquely}]