Source : Webster's Revised Unabridged Dictionary (1913)

Nacreous \Na"cre*ous\, a. [See {Nacre}.] (Zo["o]l.)
   Consisting of, or resembling, nacre; pearly.

Source : WordNet®

nacreous
     adj 1: consisting of or resembling mother-of-pearl
     2: having a play of lustrous rainbow-like colors; "an
        iridescent oil slick"; "nacreous (or pearlescent) clouds
        looking like mother-of-pearl"; "a milky opalescent (or
        opaline) luster" [syn: {iridescent}, {opalescent}, {opaline},
         {pearlescent}]