The Collaborative International Dictionary of English v.0.48:

Pyrrhic \Pyr"rhic\, n.
   1. [Gr. ?: cf. F. pyrrhique, fem.] An ancient Greek martial
      dance, to the accompaniment of the flute, its time being
      very quick.
      [1913 Webster]

   2. [L. pyrrhichius (sc. pes), Gr. ? (sc. ?): cf. F.
      pyrrhique, masc.] (Pros.) A foot consisting of two short
      syllables.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Pyrrhic \Pyr"rhic\, a. [L. pyrrhichius, Gr. ? belonging to the ?
   (sc. ?) a kind of war dance.]
   1. Of or pertaining to an ancient Greek martial dance. " ye
      have the pyrrhic dance as yet." --Byron.
      [1913 Webster]

   2. (Pros.) Of or pertaining to a pyrrhic, or to pyrrhics;
      containing pyrrhic; as, a pyrrhic verse.
      [1913 Webster]

   Pyrrhic victory [From Pyrrhus, king of Epirus.],
      (a) a victory in which the winning side sustains very
          heavy losses.
      (b) any act supposedly benefitting the actor, for which
          the costs outweight the benefits.
          [PJC]

WordNet (r) 3.0 (2006):

pyrrhic
    adj 1: of or relating to a war dance of ancient Greece; "pyrrhic
           dance movements"
    2: of or relating to or containing a metrical foot of two
       unstressed syllables; "pyrrhic verses"
    3: of or relating to or resembling Pyrrhus or his exploits
       (especially his sustaining staggering losses in order to
       defeat the Romans); "a Pyrrhic victory"
    n 1: a metrical unit with unstressed-unstressed syllables [syn:
         pyrrhic, dibrach]
    2: an ancient Greek dance imitating the motions of warfare

Moby Thesaurus II by Grady Ward, 1.0:

87 Moby Thesaurus words for "pyrrhic":
   Alexandrine, accent, accentuation, amphibrach, amphimacer,
   anacrusis, anapest, antispast, antispastic, arsis, bacchius, beat,
   cadence, cadenced, caesura, catalexis, chloriamb, chloriambus,
   colon, counterpoint, cretic, dactyl, dactylic, dactylic hexameter,
   diaeresis, dimeter, dipody, dochmiac, elegiac, elegiac couplet,
   elegiac pentameter, emphasis, epitrite, feminine caesura, foot,
   heptameter, heptapody, heroic couplet, hexameter, hexapody, iamb,
   iambic, iambic pentameter, ictus, ionic, jingle, lilt,
   masculine caesura, measure, measured, meter, metric,
   metrical accent, metrical foot, metrical group, metrical unit,
   metron, molossus, mora, movement, numbers, paeon, pentameter,
   pentapody, period, proceleusmatic, prosodic, quantity, rhythm,
   rhythmic, scanning, spondaic, spondee, sprung rhythm, stress,
   swing, syzygy, tetrameter, tetrapody, tetraseme, thesis, tribrach,
   trimeter, tripody, triseme, trochaic, trochee