Entry 2 senses Webster, 1913 Stomodaeum · Stom·o·dae·um · IPA 01 n. A part of the alimentary canal. See under Mesenteron. 1. A part of the alimentary canal. See under Mesenteron.(Anat.) See: Mesenteron 2. The primitive mouth and esophagus of the embryo of annelids and arthropods.(Zool.)