MEANING: noun: 1. A scoundrel.
2. A foul-mouthed person.
verb tr.: To disparage with abusive language.
verb intr.: To speak abusively.

ETYMOLOGY: From a blackguard, a person who did menial work in the kitchen of a noble household. Such a person may be responsible for pots and pans. Hence black + guard. Typically such persons were treated derisively. Earliest documented use: 1535. Another word originating in the kitchen to describe a person is scullion.

BLOCKGUARD - Security Officer in charge of a whole lot of prisoners

FLACKGUARD - security officer in name only, who got his job under the spoils system

LACKGUARD - unsuspecting and unprotected