trough

noun
1
a long, narrow open container for animals to eat or drink from
آخور, ظرف آب و غذا
2
a long narrow region of low air pressure between two regions of higher pressure
فرورفتگی
compare ridge
3
a period of time when the level of something is low, especially a time when a business or the economy is not growing
رکود, دوره رکود, رکود اقتصادی, افت اقتصادی
There have been peaks and troughs in the long-term trend of unemployment.
4
a low area between two waves in the sea, or two hills
فرورفتگی, دره کم‌ارتفاع, پستی