REX

[rex] n, pl rex.es or rex [modif. of F castorrex, castorex, a variety of rabbit, perh. fr. L castor beaver + rex king--more at castor, royal] (1920): an animal (as a domestic rabbit) showing a genetic recessive variation in which the guard hairs are very short or entirely lacking; esp: any of the slender domestic cats having a short curly undercoat and no guard hairs and belonging to either of two breeds