[1] : The Collaborative International Dictionary of English v.0.48

cactus \cac"tus\, n.; pl. e. cactuses, cacti -timac.
   l., a kind of cactus, gr. ??????. bot.
   any plant of the order cactacae, 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
see also:
cactuses cacti cactacae cereus cactus wren campylorhynchus 

[2] : WordNet (r) 2.0

cactus wren
     n : large harsh-voiced american wren of arid regions of the
         united states southwest and mexico

Cactus Wren >> C Words
Cactus Wren, definition of term: Cactus Wren
cactus+wren_pag1.html

Cactus >> C Words
Cactus, definition of term: Cactus
cactus_pag1.html

Wren >> W Words
Wren, definition of term: Wren
wren_pag1.html

Crab Cactus >> C Words
Crab Cactus, definition of term: Crab Cactus
crab+cactus_pag1.html

Jenny Wren >> J Words
Jenny Wren, definition of term: Jenny Wren
jenny+wren_pag1.html