A long, narrow open container for animals to eat or drink out of. The farmer filled the trough with fresh water for the horses.
A channel used to convey a liquid. The rainwater flowed down the trough into the garden.
A long, narrow depression between waves or ridges. The ship rocked gently in the trough of the waves.
A period of low economic activity or a low point in a business cycle. The economy is currently in a trough, but experts predict a recovery soon.
Meteorology: an elongated area of relatively low atmospheric pressure, often associated with unsettled weather. A cold front was approaching from the west, marked by a deep trough on the weather map.