Presphenoid \Pre*sphe"noid\, a. (Anat.) Situated in front of the sphenoid bone; of or pertaining to the anterior part of the sphenoid bone (i. e., the presphenoid bone). {Presphenoid bone} (Anat.), the anterior part of the body of the sphenoid bone in front of the basisphenoid. It is usually a separate bone in the young or fetus, but becomes a part of the sphenoid in the adult. Presphenoid \Pre*sphe"noid\, n. (Anat.) The presphenoid bone.