Source : Webster's Revised Unabridged Dictionary (1913)

Trough \Trough\, n. [OE. trough, trogh, AS. trog, troh; akin to
   D., G., & Icel. trog, Sw. tr[*a]g, Dan. trug; probably
   originally meaning, made of wood, and akin to E. tree. ? &
   241. See {Tree}, and cf. {Trug}.]
   1. A long, hollow vessel, generally for holding water or
      other liquid, especially one formed by excavating a log
      longitudinally on one side; a long tray; also, a wooden
      channel for conveying water, as to a mill wheel.

   2. Any channel, receptacle, or depression, of a long and
      narrow shape; as, trough between two ridges, etc.

   {Trough gutter} (Arch.), a rectangular or V-shaped gutter,
      usually hung below the eaves of a house.

   {Trough of the sea}, the depression between two waves.