■ noun
1》 a long, narrow open container for animals to eat or drink out of.
↘a similar container, e.g. one for growing plants.
2》 a channel used to convey a liquid.
↘a long hollow in the earth's surface.
3》 an elongated region of low barometric pressure.
4》 a hollow between two wave crests in the sea.
5》 a region around the minimum on a curve of variation of a quantity.
↘a point of low activity or achievement.
Origin
OE trog , of Gmc origin; related to tree .