The antithesis of what a good boy should be - rude, obnoxious, violent and stupid. Formed by spelling 'boy' bacwards, it was coined in England in the 18th century as it was very popular amongst upperclasses to speak backwards at the time.

The horrible moment when you realise that you have accidentally done something very slightly wrong which has very bad (usually embarassing) implications for you. This is typically the moment of realisation that you just sent a dirty text message to a close member of family, typically your mother, rather than the intended recipient.

A thugish young male.

Yobs:

Primarily British slang

Delinquent teenagers with their hoods up (as defined by the Tory party).

hooligan, ruffian

"Yobbo or yob is a slang term for an uncouth or thuggish working-class person. The word derives from a back slang reading of the word "boy" (boy or boyo reversed becomes yob or – slightly modified – yobbo)."

Definition borrowed from Wikipedia.

Mentioned in British Civilization: An Introduction by John Oakland (p.13).

A yob is a job that is tedious and/or pays a very low wage. Refers to the working conditions (and the way Mexicans would pronounce j-o-b in Spanish) of Mexican Americans.