\▐lәs-tәr\ n [MF lustre, from OI lustro, fr. lustrare to brighten, fr. L. to purify ceremonially, fr. lustrum] (ca. 1522) (1) Type of surface reflectance, or gloss, where the ratio of specular reflectance to diffuse reflectance is relatively high, but not so high as that from a perfect specular reflector (mirror). (2) Another term for gloss.