Meaning of hypolimnion

hy•po•lim•ni•on

Pronunciation: (hī"pu-lim'nē-on", -nē-un, hip"u-), [key]
— pl. -ni•a
  1. (in certain lakes) the layer of water below the thermocline.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.