A bottle containing 40 fluid ounces of malt liquor beer. The beer is of low quality and fairly cheap to buy. A bottle can run you usually between 2 and three dollars depending on brand. 40's are popular in a variety of areas and are drunken by many types of people. Gangstas will drink 40's and will sometimes pour out a little of the beer onto the ground for their dead homies. Teenagers also like to drink 40's because it is a fast way to get drunk and all the beer is in one bottle opposed to drinking several smaller 12 ounce bottles and/or cans. Some brands of beer produced in the 40 ounce variety are Clot 45, Olde English, Mickey's, and King Cobra.
"Pass me that 40 motherfucka!"
"I'm gonna pick up some 40's for tonight."