noun any channel, receptacle, or depression, of a long and narrow shape; as, trough between two ridges, ·etc.
2. trough ·add. ·noun the transverse section of a cyclonic area where the barometric pressure, neither rising nor falling, has reached its lowest point.
3. trough ·noun 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.