Any of various orchids of the genus Microtis, native to Australia, New Zealand, South-East Asia, and the Pacific region, with spikes of small, usually green flowers.
Origin
1940s.
Definition of onion orchid in US English:
onion orchid
noun
Any of various orchids of the genus Microtis, native to Australia, New Zealand, South-East Asia, and the Pacific region, with spikes of small, usually green flowers.