Source : Webster's Revised Unabridged Dictionary (1913)

Breathless \Breath"less\ (br[e^]th"l[e^]s), a.
   1. Spent with labor or violent action; out of breath.

   2. Not breathing; holding the breath, on account of fear,
      expectation, or intense interest; attended with a holding
      of the breath; as, breathless attention.

            But breathless, as we grow when feeling most.
                                                  --Byron.

   3. Dead; as, a breathless body.

Source : WordNet®

breathless
     adj 1: not breathing or able to breathe except with difficulty;
            "breathless at thought of what I had done";
            "breathless from running"; "followed the match with
            breathless interest" [syn: {dyspneic}, {dyspnoeic}, {dyspneal},
             {dyspnoeal}] [ant: {breathing}]
     2: tending to cause suspension of regular breathing; "a
        breathless flight"; "breathtaking adventure" [syn: {breathtaking}]
     3: appearing dead; not breathing or having no perceptible
        pulse; "an inanimate body"; "pulseless and dead" [syn: {inanimate},
         {pulseless}]