What is the meaning of Monocotyledon?

Any plant whose seedlings typically have one cotyledon (seed leaf) (in contrast to the two cotyledons typical of dicots), thereby belonging to the taxonomic monocots, formerly variously known as Monocotyledones, Monocotyledonae, or Liliopsida, a class in the angiosperms (Angiospermae), the flowering plants.

Source: wiktionary.org