The Collaborative International Dictionary of English v.0.48:

Pant \Pant\ (p[.a]nt), v. i. [imp. & p. p. Panted; p. pr. &
   vb. n. Panting.] [Cf. F. panteler to gasp for breath, OF.
   panteisier to be breathless, F. pantois out of breath; perh.
   akin to E. phantom, the verb prob. orig. meaning, to have the
   nightmare.]
   1. To breathe quickly or in a labored manner, as after
      exertion or from eagerness or excitement; to respire with
      heaving of the breast; to gasp.
      [1913 Webster]

            Pluto plants for breath from out his cell. --Dryden.
      [1913 Webster]

   2. Hence: To long eagerly; to desire earnestly; -- often used
      with for or after.
      [1913 Webster]

            As the hart panteth after the water brooks. --Ps.
                                                  xlii. 1.
      [1913 Webster]

            Who pants for glory finds but short repose. --Pope.
      [1913 Webster]

   3. To beat with unnatural violence or rapidity; to palpitate,
      or throb; -- said of the heart. --Spenser.
      [1913 Webster]

   4. To sigh; to flutter; to languish. [Poetic]
      [1913 Webster]

            The whispering breeze
            Pants on the leaves, and dies upon the trees.
                                                  --Pope.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

panting \panting\ n.
   The act or process of breathing heavily, usually after
   exertion.

   Syn: heaving.
        [WordNet 1.5]

   2. Any fabric used to make trousers.

   Syn: trousering.
        [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

panting \panting\ adj.
   Breathing laboriously or convulsively.

   Syn: gasping, out-of-breath(predicate), pursy, short-winded,
        winded.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

panting
    n 1: breathing heavily (as after exertion) [syn: panting,
         heaving]
    2: any fabric used to make trousers [syn: panting,
       trousering]

Moby Thesaurus II by Grady Ward, 1.0:

101 Moby Thesaurus words for "panting":
   abrupt, agog, alacritous, all agog, animated, anxious, asthmatic,
   avid, breakneck, breathing, breathless, breathlessness,
   bursting to, desirous, didder, disquiet, disquietude, dithers,
   dyspnea, eager, errhine, expiratory, fidgetiness, fidgets, flutter,
   forward, full of life, headlong, heaving, huffing, impatient,
   impetuous, impulsive, inquietude, inspiratory, keen,
   labored breathing, lively, nasal, out of breath, palpitation,
   pitapat, pitter-patter, pneumonic, precipitant, precipitate,
   precipitous, prompt, puffing, pulmonary, pulmonic, quaking, quaver,
   quavering, quick, quiver, quivering, raring to, rash, ready,
   ready and willing, respiratory, restlessness, rhinal, shakes,
   shaking, shiver, shivers, short-breathed, short-winded,
   shortness of breath, shudder, sneezy, sniffling, sniffly, sniffy,
   snoring, snorting, snuffling, snuffly, snuffy, spirited,
   sternutatory, stertorous, sudden, throb, throbbing, tremble,
   trembling, tremor, trepidation, trepidity, twitter, unrest, vital,
   vivacious, vivid, wheezing, wheezy, winded, zestful