Down The Hatch Meaning

(idiomatic) Into the mouth and down the throat, especially with regard to the consumption of a beverage.

Example: 1943 March 22, "AIR: You've Had It," Time (retrieved 7 Feb 2010):
  In Cairo, the New York Herald Tribune's correspondent, John ("Tex") O'Reilly, found U.S. soldiers no less infected with the new English language: "When two Americans are having a drink they no longer shout ‘Down the hatch!’ They raise their glasses and say ‘Cheers’ in modulated tones."
2008 Jan. 30, Paul Lukas, "Gluttonous Rite Survives Without Silverware ," New York Times (retrieved 7 Feb 2010):
  As waiters brought trays of meat, the guests reached over and harvested the pink slices with their bare hands, popping them down the hatch.