Read the dictionary definition of trough. All definitions for this word.
1. a channel along the eaves or on the roof; collects and carries away rainwater
2. a container (usually in a barn or stable) from which cattle or horses feed
3. a long narrow shallow receptacle
4. a narrow depression (as in the earth or between ocean waves or in the ocean bed)
5. a treasury for government funds
6. a concave shape with an open top
