Entry 1 sense Webster, 1913 Megacephalic /(mĕg`ȧ*sē̇*făl"ĭk)/ · Meg·a·ce·phal·ic · IPA 01 a. Large headed; -- applied to animals, and to plants when they have large flower heads. 1. Large headed; -- applied to animals, and to plants when they have large flower heads.(Biol.)