Definitions of trough:

• noun:   a long narrow shallow receptacle
• noun:   a narrow depression (as in the earth or between ocean waves or in the ocean bed)
• noun:   a channel along the eaves or on the roof; collects and carries away rainwater
• noun:   a container (usually in a barn or stable) from which cattle or horses feed
• noun:   a treasury for government funds
• noun:   a concave shape with an open top