The Collaborative International Dictionary of English v.0.48:

Jeer \Jeer\, n. [Cf. Gear.] (Naut.)
   (a) A gear; a tackle.
   (b) pl. An assemblage or combination of tackles, for hoisting
       or lowering the lower yards of a ship.
       [1913 Webster]

   Jeer capstan (Naut.), an extra capstan usually placed
      between the foremast and mainmast.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Jeer \Jeer\, v. i. [imp. & p. p. Jeered; p. pr. & vb. n.
   Jeering.] [Perh. a corrup. of cheer to salute with cheers,
   taken in an ironical sense; or more prob. fr. D. gekscheren
   to jeer, lit., to shear the fool; gek a fool (see 1st Geck)
   + scheren to shear. See Shear, v.]
   To utter sarcastic or scoffing reflections; to speak with
   mockery or derision; to use taunting language; to scoff; as,
   to jeer at a speaker.
   [1913 Webster]

         But when he saw her toy and gibe and jeer. --Spenser.

   Syn: To sneer; scoff; flout; gibe; mock.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Jeer \Jeer\, v. t.
   To treat with scoffs or derision; to address with jeers; to
   taunt; to flout; to mock at.
   [1913 Webster]

         And if we can not jeer them, we jeer ourselves. --B.
                                                  Jonson.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Jeer \Jeer\, n.
   A railing remark or reflection; a scoff; a taunt; a biting
   jest; a flout; a jibe; mockery.
   [1913 Webster]

         Midas, exposed to all their jeers,
         Had lost his art, and kept his ears.     --Swift.
   [1913 Webster]

WordNet (r) 3.0 (2006):

jeer
    n 1: showing your contempt by derision [syn: jeer, jeering,
         mockery, scoff, scoffing]
    v 1: laugh at with contempt and derision; "The crowd jeered at
         the speaker" [syn: jeer, scoff, flout, barrack,
         gibe]

Moby Thesaurus II by Grady Ward, 1.0:

97 Moby Thesaurus words for "jeer":
   Parthian shot, affront, aspersion, atrocity, back answer, barrack,
   boo, brickbat, bullyrag, call names, catcall, caustic remark,
   chaff, comeback, contempt, contumely, crack, cut, cut at,
   cutting remark, decry, deride, derision, despite, dig, dig at,
   dishonor, disoblige, dump, dump on, enormity, fleer, fleer at,
   flout, flouting, foolery, gibe, gibe at, gibing retort, gird,
   give offense to, hiss, hoot, humiliate, humiliation,
   hurl a brickbat, indignity, injury, insult, jab, jab at, jape,
   jeer at, jeering, jest, jibe, jibe at, knock, leg-pull,
   make fun of, mock, mockery, obloquy, offend, offense, outrage,
   parting shot, pooh, pooh-pooh, put down, put-down, put-on, quip,
   rag, rail at, rally, rank out, revile, ridicule, roast,
   rude reproach, scoff, scoff at, scout, scurrility, short answer,
   slam, slap, slap at, sneer, sneer at, swipe, taunt,
   treat with indignity, twit, uncomplimentary remark,
   verbal thrust