Entry 1 sense Webster, 1913 dicotyledonous /(dī̇*kŏt`ĭ*lĕd"ŭn*ŭs)/ · di·cot·y·led·on·ous · IPA 01 a. Having two cotyledons or seed lobes; as, a dicotyledonous plant. 1. Having two cotyledons or seed lobes; as, a dicotyledonous plant.(Bot.)