The Collaborative International Dictionary of English v.0.48:
Cactus \Cac"tus\, n.; pl. E. Cactuses, Cacti (-t[imac]).
[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
Cactus wren (Zool.), an American wren of the genus
Campylorhynchus, of several species.