Green’s Dictionary of Slang

mob adj.

[mob n.2 (3)]

(US) related to a criminal gang, esp. the US Mafia, or its culture and lifestyle.

implied in Mob Town
implied in mob guy
[US]Monteleone Criminal Sl. (rev. edn) 156: mob head A gang leader [...] mob moll A female gangster.
[US]E. Reid Shame of N.Y. 5: The Mob and the mob politicians controlled by the organization really believe that they are indispensable to the people.
[US]E. Wilson Show Business Nobody Knows 137: One of the mob places was the old Greenwich Village Inn in Sheridan Square [...] It was operated strictly as a front ‘to keep some of the boys working in a legitimate business’.
[US]C. Hiaasen Skin Tight 22: They think it’s a mob hit?
[US]B. Hamper Rivethead (1992) 9: Denny better watch his shit cuz these mob pricks were no one to try and slip a change-up by.
[US]C. Fleming High Concept 128: A New Yorker with a shady past and a family history of mob ties.
[UK]Guardian Editor 7 Jan. 12: To get the most out of Donnie Brasco, it helps to see it as a primer in Mob lingo.
[US]A. Steinberg Running the Books 373: Boat recounted the catalog of his old bank robberies, mob jobs [etc].
[US]D. Winslow The Force [ebook] An armed confrontation with three wiseguys in a known mob hangout.
[US]C. Stella Joey Piss Pot 5: ‘[Y]ou owned a bar in a mob haven and your brother-in-law was a wiseguy himself’.

In compounds

mob guy (n.) (also mob boy, mob gee, mob ghee)(US Und.)

1. a member of a criminal gang.

[US]G. Milburn ‘Convicts’ Jargon’ in AS VI:6 440: mob gee, n. A member of a mob.
[US]Monteleone Criminal Sl. (rev. edn) 156: mob gee A gangster.
[US]Goldin et al. DAUL 139/1: Mob-ghee. One who works with a gang in preference to operating alone; a member of a criminal gang.
[US]E. Torres Carlito’s Way 122: You’re not a mob guy; you don’t owe them a thing.
[US]E. Torres Q&A 20: He’s a regular mob guy, a boss.

2. a member of the US Mafia; thus. ext. to counterparts in other countries.

[US]La Motta, Carter & Savage Raging Bull 26: I figured I’d show the mob boys they weren’t dealing with a couple of fairies in me and Pete.
[US]P. Hamill Dirty Laundry 152: The bank was essentially a laundry, used by mob guys and C.I.A. types.
[US]C. Hiaasen Double Whammy (1990) 62: Dennis flew down two mob guys from Queens. Offered them eighty grand to bump off Dickie.
[US](con. 1970s) J. Pistone Donnie Brasco (2006) 353: They could say they recognize us as mob guys.
[Aus]M.B. ‘Chopper’ Read How to Shoot Friends 34: He thought he was a real mob guy, just like in the movies.
[US]D. Winslow Border [ebook] [T]he humor of it, two mob guys and the head of the NYPD’s Narcotics Division wanting him to do the same thing.
[Aus]A. Nette Orphan Road 90: ‘New York got involved, the body count went up, mob guys started cutting deals with the Feds’.
Mob Town (n.) (also Mob City)

(US) Baltimore, Maryland.

[US]A. Greene Glance at N.Y. 97: Baltimore has been emphatically called the Mob-City.
[UK]Farmer Americanisms 47: Mobtown. — The city of Baltimore. This place has always been, and still is, notorious for the gangs of roughs and rowdies which infest its streets [DA].
[US]Sat. Eve. Post 11 May 15/2: Baltimore [...] in an earlier time when it was only moderately industralized [...] was known, with good reason, as ‘Mob-town’ [DA].