A member of a gang. "Gangsters" refers back to the 1920s during Prohibition era when alcohol was illegal. Gangsters would bootleg alcohol to be sold at speakeasies. In the 21st century, the new term is "Gangsta," which is really a person, usually a lower-middle class or poor African-American male, who dons the title to intimidate others. Often in the right situations "gangstas" are the first to run away in scenarios that they claim to always see.
Mary: Did you see that gangster film?
John: "Scarface?" Yeah, that's a classic!
Travis: Hey, yo! I'm a true gangsta! I own a gun and have been capped.