n. [ Gr. fw^s light + fai`nein to show. ] (Physiol.) A luminous impression produced through excitation of the retina by some cause other than the impingement upon it of rays of light, as by pressure upon the eyeball when the lids are closed. Cf. After-image. [ 1913 Webster ]

n. [ F. sphène, fr. Gr. sfh`n a wedge. ] (Min.) A mineral found usually in thin, wedge-shaped crystals of a yellow or green to black color. It is a silicate of titanium and calcium; titanite. [ 1913 Webster ]

a. [ Sphenoid + ethmoid. ] (Anat.) Of or pertaining to both the sphenoidal and the ethmoidal regions of the skull, or the sphenethmoid bone; sphenethmoidal. [ 1913 Webster ]

Sphenethmoid bone (Anat.), a bone of the skull which surrounds the anterior end of the brain in many amphibia; the girdle bone. [ 1913 Webster ]

n. (Anat.) The sphenethmoid bone. [ 1913 Webster ]

a. (Anat.) Relating to the sphenoethmoid bone; sphenoethmoid. [ 1913 Webster ]

n. [ Gr. zygo`n a yoke + &unr_; a wedge. ] (Anat.) A median process on the front part of the neural arch of the vertebrae of most snakes and some lizards, which fits into a fossa, called the zygantrum, on the back part of the arch in front. [ 1913 Webster ]