WordWeb Online

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"
   - dyspneic, dyspnoeic, dyspneal, dyspnoeal
    
2. Tending to cause suspension of regular breathing
   "a breathless flight"
   - breathtaking
    
3. Appearing dead; not breathing or having no perceptible pulse
   - inanimate, pulseless
    
4. Breathing heavily (as after exertion)
   - out of breath, gasping, short-winded

See also: asphyxiating, blown, breathlessly, breathlessness, dead, exciting, pursy [archaic], short-winded, smothering, suffocating, suffocative, unventilated, winded

Antonym: breathing

Encyclopedia: Breathless