Usually said to reiterate the importance of drinking. Just saying "drink" once doesn't convey the sense importance surrounding our drinking culture. Said twice, with some gusto,a party shall evolve, like magic.
Can be compounded by saying "drink" as many times until it sounds something like Drinkdrinkdrkkddir
1) any beverage, most often one which is or contains alcohol.
2) "in the drink" - referring to something that is over and done with.
(from the golf term, a small body of water on the course where the ball will sometimes fall into).
Something that wives keep count of when you are at a party.
For example, after a couple of hours laughing and joking with the men, your wife will sidleup to you and say in a very accusing tone of voice "That's your fourth drink, you know".