n.
     - a long, narrow open container for animals to eat or drink out of. 
▸a similar container, e.g. one for growing plants.
 - a channel used to convey a liquid. 
▸a long hollow in the earth's surface.
 - an elongated region of low barometric pressure.
 - a hollow between two wave crests in the sea.
 - a region around the minimum on a curve of variation of a quantity. 
▸a point of low activity or achievement.
 
v.
 informal eat greedily.
 
  Etymology
  OE trog, of Gmc origin; rel. to tree.