trough
n
1 long narrow open box for animals to feed or drink from 饲料槽; 饮水槽. =>illus at pig 见 pig 插图.
2 shallow channel that allows water, etc to drain away 排水沟.
3 low area between two waves or ridges 波谷; 低谷. =>illus at surf 见 surf 插图.
4 (in meteorology) long narrow region of low atmospheric pressure between two regions of higher pressure (气象)低压槽. Cf 参看 ridge 3.