The Collaborative International Dictionary of English v.0.48:

Bracken \Brack"en\, n. [OE. braken, AS. bracce. See 2d Brake,
   n.]
   A brake or fern. --Sir W. Scott.
   [1913 Webster]

WordNet (r) 3.0 (2006):

bracken
    n 1: fern of southeastern Asia; not hardy in cold temperate
         regions [syn: bracken, Pteridium esculentum]
    2: large coarse fern often several feet high; essentially weed
       ferns; cosmopolitan [syn: bracken, pasture brake,
       brake, Pteridium aquilinum]