The Collaborative International Dictionary of English v.0.48:

Jab \Jab\ (j[a^]b), v. t. [Cf. Job.]
   To thrust; to stab; to punch. See Job, v. t. [Scot. &
   Colloq. U. S.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Jab \Jab\, n.
   A thrust or stab. [Scot. & Colloq. U. S.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

jab
    n 1: a sharp hand gesture (resembling a blow); "he warned me
         with a jab with his finger"; "he made a thrusting motion
         with his fist" [syn: jab, jabbing, poke, poking,
         thrust, thrusting]
    2: a quick short straight punch
    3: the act of touching someone suddenly with your finger or
       elbow; "she gave me a sharp dig in the ribs" [syn: dig,
       jab]
    v 1: poke or thrust abruptly; "he jabbed his finger into her
         ribs" [syn: jab, prod, stab, poke, dig]
    2: strike or punch with quick and short blows
    3: stab or pierce; "he jabbed the piece of meat with his pocket
       knife" [syn: stab, jab]

Moby Thesaurus II by Grady Ward, 1.0:

161 Moby Thesaurus words for "jab":
   Parthian shot, assault, back answer, bang, barrack, bash, bat,
   bear, bear upon, bearing, beating, belt, biff, blow, bonk, boost,
   buck, bull, bulldoze, bump, bump against, bunt, butt, butt against,
   caustic remark, chaff, chop, clap, clip, clobber, clout, clump,
   coldcock, comeback, crack, cram, crowd, cut, cut at,
   cutting remark, dash, deal, deal a blow, deck, dig, dig at, dint,
   drive, drub, drubbing, drumming, dump, dump on, elbow, feint,
   fetch, fetch a blow, fleer, flout, foolery, force, fusillade, gibe,
   gibing retort, goad, head, hit, hit a clip, home thrust, hurtle,
   hustle, jab at, jam, jape, jeer, jest, jog, joggle, jolt, jostle,
   knock, knock cold, knock down, knock out, leg-pull, let have it,
   lick, lunge, mock, nudge, parting shot, pass, paste, pelt,
   pile drive, plunk, poke, pooh, pooh-pooh, pound, press, pressure,
   prod, punch, push, put down, put-down, put-on, quip, rail at,
   rally, ram, ram down, rank out, rap, rattle, revile, rude reproach,
   run, run against, scoff, scout, scurrility, shake, short answer,
   shoulder, shove, slam, slap, slap at, slog, slug, smack, smash,
   smite, snap, sneer, sneer at, soak, sock, stab, stress, strike,
   strike at, stroke, swat, swing, swipe, tamp, tattoo, taunt, thrust,
   thump, thwack, twit, verbal thrust, wallop, whack, wham, whop,
   yerk