The Collaborative International Dictionary of English v.0.48:

Hound's-tongue \Hound's"-tongue`\, n. [AS. hundes tunge.] (Bot.)
   A biennial weed (Cynoglossum officinale), with soft
   tongue-shaped leaves, and an offensive odor. It bears nutlets
   covered with barbed or hooked prickles. Called also
   dog's-tongue.
   [1913 Webster]