What is "meromictic lake"

n. any lake whose waters are permanently stratified and do not completely circulate

A meromictic lake has layers of water that do not intermix. In ordinary, " holomictic" lakes, at least once each year, there is a physical mixing of the surface and the deep waters.

The term "meromictic" was coined by the Austrian Ingo Findenegg in 1935, apparently based on the older word "holomictic". The concepts and terminology used in describing meromictic lakes were essentially complete following some additions by G. Evelyn Hutchinson in 1937.