RhymeZone: nobbler definitions

Definitions of nobbler:

noun: A person who interferes with a racehorse or greyhound in order to prevent it from winning a race.
noun: (Australia, obsolete) A serving of beer or spirits.
noun: (UK, obsolete) A thimbleman's or cardsharp's accomplice or shill, who poses as a player of the game to suggest that it is easy to win.

(Definitions from Wiktionary)