The Collaborative International Dictionary of English v.0.48:

friar's-cowl \friar's-cowl\, friar's-cowls \friar's-cowls\n.
   (Bot.)
   A tuberous perennial (Arisarum vulgare) having a
   cowl-shaped maroon or violet-black spathe; -- found in the
   Mediterranean, Canaries, and Azores.

   Syn: friars' cowl, Arisarum vulgare.
        [WordNet 1.5]