The Collaborative International Dictionary of English v.0.48:
Trough \Trough\ (tr[o^]f), 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. [root]63 & 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.
3. (Meteor.) The transverse section of a cyclonic area where
the barometric pressure, neither rising nor falling, has
reached its lowest point.
[Webster 1913 Suppl.]
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.