Any plant of the order Cactacæ, 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.
- Any of various succulent, spiny, usually leafless plants native mostly to arid regions of the New World, having variously colored, often showy flowers with numerous stamens and petals.
- Any of several similar plants.