acotyledonPronunciation: /əˌkɒtɪˈliːd(ə)n/Definition of acotyledon noun Botany a plant with no distinct seed leaves, especially a fern or moss. Derivatives acotyledonous adjective Origin: mid 18th century: from modern Latin plural acotyledones (see a-1, cotyledon)acotyledon in other Oxford dictionaries Definition of acotyledon in the US English dictionary