any fern of the genus Osmunda: large ferns with creeping rhizomes; naked sporangia are on modified fronds that resemble flower clusters
source: WordNet 3.0
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.