Source : Webster's Revised Unabridged Dictionary (1913)

Lignum-vitae \Lig"num-vi"tae\ (-v[imac]"t[=e]), n. [L., wood of
   life; lignum wood + vita, genitive vit[ae], life.] (Bot.)
   A tree ({Guaiacum officinale}) found in the warm latitudes of
   America, from which the {guaiacum} of medicine is procured.
   Its wood is very hard and heavy, and is used for various
   mechanical purposes, as for the wheels of ships' blocks,
   cogs, bearings, and the like. See {Guaiacum}.

   Note: In New Zealand the {Metrosideros buxifolia} is called
         lignum-vit[ae], and in Australia a species of {Acacia}.
         The bastard lignum-vit[ae] is a West Indian tree
         ({Sarcomphalus laurinus}).

Source : WordNet®

Guaiacum officinale
     n : small evergreen tree of Caribbean and southern Central
         America to northern South America; a source of lignum
         vitae wood, hardest of commercial timbers, and a
         medicinal resin [syn: {lignum vitae}]