Definition of "Coma" :

noun: a state of deep and often prolonged unconsciousness; usually the result of disease or injury

noun: (astronomy) the luminous cloud of particles surrounding the frozen nucleus of a comet; forms as the comet approaches the sun and is warmed

noun: (botany) a usually terminal tuft of bracts (as in the pineapple) or tuft of hairs (especially on certain seeds)