Source : Webster's Revised Unabridged Dictionary (1913)

Marrubium \Mar*ru"bi*um\, n. [L.] (Bot.)
   A genus of bitter aromatic plants, sometimes used in
   medicine; hoarhound.

Source : WordNet®

Marrubium
     n : Old World aromatic herbs: horehound [syn: {genus Marrubium}]