Meaning of acotyledon

a•cot•y•le•don

Pronunciation: (ā'kot"l-ēd'n, ā-kot"-), [key]
— n.
  1. a plant without cotyledons, therefore one belonging to a group lower than the seed plants.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.