Definition of: blackguard

(blag′ərd, -ärd) noun
A low, vicious fellow; a scoundrel.
—v.t. To revile; vilify.
—v.i. To act like a blackguard.
—adjective Of or like a blackguard; base; vile: also black′guard·ly. [<black guard, orig., the scullions and low menials of a great house or army; later applied to any base person]
—black′guard·ism noun