From Moby Thesaurus II by Grady Ward, 1.0 :
21 Moby Thesaurus words for "cactus":
bramble, brier, bristle, burr, catchweed, cleavers, goose grass,
needle, nettle, pine needle, prickle, quill, spicule, spiculum,
spike, spikelet, spine, sticker, thistle, thorn, yucca