Word parts mob + -ster Pronunciation (UK) IPA (key): /ˈmɒb.stə/ (US) IPA (key): /ˈmɑb.stɚ/ Audio (UK)(file) Noun Singular mobster Plural mobsters (countable) A mobster is someone who is part of the Mafia or a similar organized criminal group Wikiwand - on Seamless Wikipedia browsing. On steroids.Remove ads