I. ˈsfēˌnȯid adjective
also sphe·noi·dal (ˈ)sfē|nȯid ə l
Etymology: sphenoid, from New Latin sphenoides, from Greek sphēnoeidēs wedge-shaped, from sphēn wedge + -oeidēs oid; sphenoidal, from New Latin sphenoidalis, from Greek sphēnoeidēs + Latin -alis -al — more at spoon
1. : of, relating to, or situated in the region of a compound bone of the base of the cranium of various vertebrates formed by the fusion of several bony elements with the basisphenoid and in man consisting of a median body from whose sides extend a pair of broad curved winglike expansions in front of which is another pair of much smaller triangular lateral processes while ventrally two large deeply cleft processes extend downward
a sphenoid sinus
2. usually sphenoidal
a. : relating to or resembling a sphenoid : wedge-shaped
b. : having such symmetry that the general form is a sphenoid — used of a monoclinic crystal with a diad axis of symmetry
II. noun
( -s )
1. : a sphenoid bone
2.
a. : a wedge-shaped open form in the monoclinic system of crystallization consisting of two faces related by a diad axis of symmetry — compare dome
b. : disphenoid