| an erect stiff cactus, Echinocereus pectinatus rigidissimus, of Arizona and Mexico, having a cylindrical body, numerous interlocking spines, and pink flowers. |
| rainbow cactus n. Either of two spiny cylindrical varieties of cactus of the southwestern United States and Mexico, Echinocereus pectinatus var. neomexicanus, having yellow flowers, or E. pectinatus var. rigidissimus, having showy magenta flowers. |