Cactus \Cac"tus\, n.; pl. E. {Cactuses}, {Cacti} (-t[=i]). [L., a kind of cactus, Gr. ??????.] (Bot.) Any plant of the order {Cactac[ae]}, as the prickly pear and the night-blooming cereus. See {Cereus}. They usually have leafless stems and branches, often beset with clustered thorns, and are mostly natives of the warmer parts of America. {Cactus wren} (Zo["o]l.), an American wren of the genus {Campylorhynchus}, of several species.