The Collaborative International Dictionary of English v.0.48:

Breadroot \Bread`root"\, n. (Bot.)
   The root of a leguminous plant (Psoralea esculenta), found
   near the Rocky Mountains. It is usually oval in form, and
   abounds in farinaceous matter, affording sweet and palatable
   food.
   [1913 Webster]

   Note: It is the Pomme blanche of Canadian voyageurs.
         [1913 Webster]

WordNet (r) 3.0 (2006):

breadroot
    n 1: densely hairy perennial of central North America having
         edible tuberous roots [syn: breadroot, Indian
         breadroot, pomme blanche, pomme de prairie, Psoralea
         esculenta]