look up any word, like fleek:
 
1.
The best overall college beer. Good taste, yet you can drink it till the sun comes up, and its only like 13 bucks for 30 of them.
I woke up at 1pm and drank keystone till 6am while smoking blunts of the chronic every couple hours but didnt pass out because keystone allows you to consume record amounts of beer and feel fine the next day.
by Chuck January 06, 2005
 
2.
A very inexpensive beer purchased and consumed by trailer trash and frat boys everywhere. Probably manufactured in prison toilets.
Matt: "Hey Ryan, I have a couple of bucks. Enough for some Keystone! Let's go get wasted and make out with each other!"
by Ice Cold January 22, 2005
 
3.
usually refering to keystone light...

Introduced in 1989, Keystone Light is a light-bodied, crisp, smooth and drinkable beer. Keystone Light is available nationwide in cans, bottles and kegs.  Keystone Light is 4.2 percent alcohol by volume and has 104 calories per 12-ounce serving.

Awards

2005 Great American Beer Festival bronze medalist, American-Style Light Lager
2003 North American Beer Awards bronze medalist, American Light Lager
1991 Great American Beer Festival gold medalist, American Light Lager
1991 Great American Beer Festival bronze medalist, American Lager

(coors brewing company web site)
Mike: i need 4 more bucks to pick up a case of keystone

Ike: ok here's 4, i get half though
by FIREH20 November 15, 2006
 
4.
Cheap beer, it's actually coors light brewed 1/1,000,000 of a degree of thus decreasing the beverage in value so it's about 10 bucks a case.
I drank a bunch of keystone and I wrecked my car into that nukkas crib homie!
by the big neptizzle August 14, 2003
 
5.
The central wedge-shaped stone of an arch that locks its parts together.
Without the keystone the arch would fall down.
by meep116 July 27, 2006