The Collaborative International Dictionary of English v.0.48:

Mob \Mob\, n. [L. mobile vulgus, the movable common people. See
   Mobile, n.]
   1. The lower classes of a community; the populace, or the
      lowest part of it.
      [1913 Webster]

            A cluster of mob were making themselves merry with
            their betters.                        --Addison.
      [1913 Webster]

   2. Hence: A throng; a rabble; esp., an unlawful or riotous
      assembly; a disorderly crowd.
      [1913 Webster]

            The mob of gentlemen who wrote with ease. --Pope.
      [1913 Webster]

            Had every Athenian citizen been a Socrates, every
            Athenian assembly would still have been a mob.
                                                  --Madison.
      [1913 Webster]

            Confused by brainless mobs.           --Tennyson.
      [1913 Webster]

   3. A criminal organization or organized criminal gangs,
      collectively; the Mafia; the syndicate; as, he was a
      lawyer for the mob.
      [PJC]

   Mob law, law administered by the mob; lynch law.

   Swell mob, well dressed thieves and swindlers, regarded
      collectively. [Slang] --Dickens.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Mob \Mob\, v. t. [imp. & p. p. Mobbed; p. pr. & vb. n.
   Mobbing.]
   To crowd about, as a mob, and attack or annoy; as, to mob a
   house or a person.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Mob \Mob\, n. [See Mobcap.]
   A mobcap. --Goldsmith.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Mob \Mob\, v. t.
   To wrap up in, or cover with, a cowl. [R.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

mob
    n 1: a disorderly crowd of people [syn: mob, rabble, rout]
    2: a loose affiliation of gangsters in charge of organized
       criminal activities [syn: syndicate, crime syndicate,
       mob, family]
    3: an association of criminals; "police tried to break up the
       gang"; "a pack of thieves" [syn: gang, pack, ring,
       mob]
    v 1: press tightly together or cram; "The crowd packed the
         auditorium" [syn: throng, mob, pack, pile, jam]

Moby Thesaurus II by Grady Ward, 1.0:

180 Moby Thesaurus words for "mob":
   Black Hand, Bund, Cosa Nostra, Rochdale cooperative, a mass of,
   a world of, age group, alliance, army, assemblage, association,
   axis, band, battalion, bevy, bloc, body, brigade, bunch, cabal,
   cadre, camarilla, camp, canaille, carpet, cast, cell,
   charmed circle, chew out, circle, clan, clique, closed circle,
   cloud, cluster, clutter, coalition, cohort, cohue, college,
   combination, combine, common market, company, complement,
   confederacy, confederation, consumer cooperative, contingent,
   cooperative, cooperative society, corps, coterie, council, covey,
   credit union, crew, crowd, crush, customs union, deluge,
   detachment, detail, division, dregs, economic community, elite,
   elite group, faction, federation, fleet, flight, flock, flocks,
   flood, free trade area, galaxy, gang, gangdom, gangland, group,
   grouping, groupment, hail, heap, herd, hive, horde, host,
   ignobile vulgus, in-group, ingroup, inner circle, jam, junta,
   junto, large amount, lash, league, legion, lots, machine, many,
   many-headed multitude, mass, masses, masses of, mobile vulgus,
   movement, muchness, multitude, nest, numbers, organized crime,
   out-group, outfit, pack, panoply, partnership, party, peer group,
   phalanx, platoon, plurality, political machine, posse, press,
   proletariat, push, quantities, quite a few, rabble,
   ragtag and bobtail, rail, rate, regiment, riffraff, ring, rout,
   row, ruck, salon, scores, scum, set, shoal, society, spate, squad,
   stable, string, swarm, team, the Mafia, the common herd, the crowd,
   the great unnumbered, the great unwashed, the herd, the hoi polloi,
   the horde, the majority, the many, the masses, the mob,
   the multitude, the rackets, the syndicate, the underworld, throng,
   tidy sum, trash, tribe, troop, troupe, union, unwashed, we-group,
   wing, worlds of



V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

MOB
       Memory Ordering Buffer (Intel, CPU)