Meaning of deep scattering layer

deep' scat'tering lay"er

Pronunciation: [key]
— Oceanog. Oceanog.
  1. a zone of biological origin within the ocean, at a depth of 900–1200 ft. (270–360 m), which scatters sounding echoes.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.