from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. coiled in the plane (as opposed to helical)
from The Century Dictionary and Cyclopedia
- Coiled in one plane, like a watch-spring or flat spiral, as the antlia of a butterfly; whorled in discoid form, as a shell of the genus Planorbis. Also planospiral.
Sorry, no etymologies found.