hypolimnion

 
Pronunciation: /ˌhʌɪpə(ʊ)ˈlɪmnɪən/

noun (plural hypolimnia /-nɪə/)

  • the lower layer of water in a stratified lake, typically cooler than the water above and relatively stagnant.

Origin:

early 20th century: from hypo- 'below' + Greek limnion (diminutive of limnē 'lake')