The Collaborative International Dictionary of English v.0.48:

Olusatrum \O*lu"sa*trum\, n. [L. holusatrum, olusatrum; olus
   garden herb + ater black.] (Bot.)
   An umbelliferous plant, the common Alexanders of Western
   Europe (Smyrnium Olusatrum).
   [1913 Webster]