(1):
(n.) A vagrant; a bootblack; a gamin.
(2):
(n.) A person of stained or low character, esp. one who uses scurrilous language, or treats others with foul abuse; a scoundrel; a rough.
(3):
(n.) The scullions and lower menials of a court, or of a nobleman's household, who, in a removal from one residence to another, had charge of the kitchen utensils, and being smutted by them, were jocularly called the "black guard"; also, the servants and hangers-on of an army.
(4):
(v. t.) To revile or abuse in scurrilous language.
(5):
(a.) Scurrilous; abusive; low; worthless; vicious; as, blackguard language.
(6):
(n.) The criminals and vagrants or vagabonds of a town or community, collectively.