Cheating, changing side, or beating. I’ll trim his jacket; I’ll thresh him. To be trimmed; to be shaved; I’ll just step and get trimmed.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Trim Tram * TrineNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes