Source : Webster's Revised Unabridged Dictionary (1913)

Pomme blanche \Pomme` blanche"\ [F., literally, white apple.]
   The prairie turnip. See under {Prairie}.

Source : WordNet®

pomme blanche
     n : densely hairy perennial of central North America having
         edible tuberous roots [syn: {breadroot}, {Indian
         breadroot}, {pomme de prairie}, {Psoralea esculenta}]