WordNet (r) 3.0 (2006):

helmet orchid
    n 1: any of numerous orchids of the genus Pterostylis having
         leaves in a basal rosette and green flowers often striped
         purple or brown or red with the dorsal sepal incurved to
         form a hood [syn: helmet orchid, greenhood]
    2: any of several orchids of the genus Coryanthes having racemes
       of a few musky-scented waxy flowers with a helmet-shaped lip
       process [syn: helmetflower, helmet orchid]