Gangster's gun is a term used to describe a firearm typically associated with criminals. The three crossword solutions for this term are GAT, ROSCOE, and ROD. GAT is a slang term for a gun, usually a revolver, that was popularized in the 1920s. ROSCOE is another slang term for a gun, usually a revolver, that was popularized in the 1930s. ROD is a slang term for a gun, usually a pistol, that was popularized in the 1940s.