1. A state of deep, often prolonged unconsciousness, usually resulting from injury or illness
   "The patient's coma persisted for weeks after the accident";
   - comatoseness
    
2. (botany) a usually terminal tuft of bracts (as in the pineapple) or tuft of hairs (especially on certain seeds)
   "The dandelion seeds had a feathery coma that helped them disperse in the wind"
    
3. (astronomy) the luminous cloud of particles surrounding the frozen nucleus of a comet; forms as the comet approaches the sun and is warmed
   "The comet's coma grew brighter as it neared the sun"; "Astronomers studied the composition of the coma to learn about the comet's origins"
    
4. (optics) an aberration giving a V-shaped flare to an image (e.g. a star in an astronomical observation)
   "The telescope's coma aberration caused stars near the edge of the field to appear distorted"

Derived forms: comae, comas

Type of: cloud, tuft, tussock, unconsciousness

Part of: comet

Encyclopedia: Coma, post-head injury