Entry 1 sense Webster, 1913 dicotyledon /(dī̇*kŏt`ĭ*lē"dŭn)/ · di·cot·y·le·don · IPA 01 n. A plant whose seeds divide into two seed lobes, or cotyledons, in germinating. 1. A plant whose seeds divide into two seed lobes, or cotyledons, in germinating.(Bot.) Syn. dicot, dicotyl.