The Collaborative International Dictionary of English v.0.48:

Osmund \Os"mund\, n. (Bot.)
   A fern of the genus Osmunda, or flowering fern. The most
   remarkable species is the osmund royal, or royal fern
   (Osmunda regalis), which grows in wet or boggy places, and
   has large bipinnate fronds, often with a panicle of capsules
   at the top. The rootstock contains much starch, and has been
   used in stiffening linen.
   [1913 Webster]

WordNet (r) 3.0 (2006):

osmund
    n 1: any fern of the genus Osmunda: large ferns with creeping
         rhizomes; naked sporangia are on modified fronds that
         resemble flower clusters [syn: flowering fern, osmund]