Source : Webster's Revised Unabridged Dictionary (1913)

Benthos \Ben"thos\, n. [NL., fr. Gr. ? depth of the sea.]
   The bottom of the sea, esp. of the deep oceans; hence (Bot. &
   Zo["o]l.), the fauna and flora of the sea bottom; -- opposed
   to {plankton}.

Source : WordNet®

benthos
     n 1: a region including the bottom of the sea and the littoral
          zones [syn: {benthic division}, {benthonic zone}]
     2: organisms (plants and animals) that live at or near the
        bottom of a sea