from The American Heritage® Dictionary of the English Language, 4th Edition
- n. The layer of water in a thermally stratified lake that lies below the thermocline, is noncirculating, and remains perpetually cold.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. the perpetually cold layer of water that lies beneath the thermocline of a thermally stratified lake
hypo- + Greek limnē, lake, pool.(American Heritage® Dictionary of the English Language, Fourth Edition)
From Ancient Greek ὑπο- (hypo-), combining form of ὑπό (hypó, "under") + λιμνίον (limnion), diminutive of λίμνη (limnē, "lake"). (Wiktionary)