The Collaborative International Dictionary of English v.0.48:

Bear's-breech \Bear's"-breech`\, bear's-breeches
\bear's"-breech`es\, n.
   1. (Bot.) The English cow parsnip (Heracleum sphondylium)
      --Dr. Prior.
      [1913 Webster]

   2. a widely cultivated southern European acanthus (Acanthus
      mollis) with whitish purple-veined flowers. See
      Acanthus, n., 1.

   Syn: bear's breech, bear's-breech, bear's breeches, sea
        holly.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

Acanthus mollis
    n 1: widely cultivated southern European acanthus with whitish
         purple-veined flowers [syn: bear's breech, bear's
         breeches, sea holly, Acanthus mollis]