Merriam-Webster Collegiate Dictionary - nopal

 noun  (plural ~s or ~es)  Etymology: Spanish, from Nahuatl nohpalli  Date: 1730  1. any of a genus (Nopalea) of cacti of Mexico and Central America that differ from the prickly pears in having erect petals and scarlet flowers with the stamens much longer than the petals; broadly prickly pear  2. a fleshy young tender stem segment of the prickly pear cactus (especially Opuntia ficus-indica) or the ~ cactus used as food