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]