Emily Dickinson Lexicon

CO'MA, n.² [L. from Gr. κομη, a head of hair.]

1. In botany, a species of bract, terminating the stem of a plant, in a tuft or bush; as in Crown-imperial. – Martyn.
2. In astronomy, hairiness; the hairy appearance that surrounds a comet, when the earth or the spectator is between the comet and the sun.