Source : Webster's Revised Unabridged Dictionary (1913)

Wolf's-milk \Wolf's"-milk`\, n. (Bot.)
   Any kind of spurge ({Euphorbia}); -- so called from its acrid
   milky juice.

Euphorbia \Eu*phor"bi*a\, n. [NL., fr. L. euphorbea. See
   {Euphorrium}.] (Bot.)
   Spurge, or bastard spurge, a genus of plants of many species,
   mostly shrubby, herbaceous succulents, affording an acrid,
   milky juice. Some of them are armed with thorns. Most of them
   yield powerful emetic and cathartic products.

Source : WordNet®

Euphorbia
     n : type genus of the Euphorbiaceae: very large genus of diverse
         plants all having milky juice [syn: {genus Euphorbia}]