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
   America.
   [1913 Webster]

   Cactus wren (Zool.), an American wren of the genus
      Campylorhynchus, of several species.
      [1913 Webster]

WordNet (r) 3.0 (2006):

cactus
    n 1: any succulent plant of the family Cactaceae native chiefly
         to arid regions of the New World and usually having spines

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



U.S. Gazetteer Places (2000):

Cactus, TX -- U.S. city in Texas
   Population (2000):    2538
   Housing Units (2000): 820
   Land area (2000):     2.040434 sq. miles (5.284699 sq. km)
   Water area (2000):    0.000000 sq. miles (0.000000 sq. km)
   Total area (2000):    2.040434 sq. miles (5.284699 sq. km)
   FIPS code:            11692
   Located within:       Texas (TX), FIPS 48
   Location:             36.046124 N, 102.002251 W
   ZIP Codes (1990):
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Cactus, TX
    Cactus