| Noun | 1. | Thelypteris dryopteris - bright blue-green fern widely distributed especially in damp acid woodlands of temperate northern hemisphere fern - any of numerous flowerless and seedless vascular plants having true roots from a rhizome and fronds that uncurl upward; reproduce by spores genus Gymnocarpium, Gymnocarpium - oak ferns: in some classification systems included in genus Thelypteris |