1. In seafaring, a young male sailor in Her Majesty's Navy, usually of slender disposition who was designated to sit on a peg to keep his anus loose for penetration by the other sailors.
2. In more modern times, a derogatory term denoting a sissy, a fag, or a feminine sailor.
After a long day swabbing the decks, a visit to Billy the peg boy proved to be quite relaxing and enjoyable for Captain Wollingsworth.