cactus

Concise Oxford English Dictionary © 2008 Oxford University Press:
cactus/ˈkaktəs/

▶noun (pl. cacti /-tʌɪ/ or cactuses) a succulent plant of a large family native to arid regions of the New World, with a thick fleshy stem which typically bears spines, lacks leaves, and has brilliantly coloured flowers. [Family Cactaceae.]

– derivatives
cactaceous adjective.

– origin C17 (in the sense ‘cardoon’): from L., from Gk kaktos ‘cardoon’.