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1.
4-o
A 4-o is another word for a fourty ounce beer. Pronounced four-o or depenting on regional origin fo-o
Let hit the sto and get a 4-o.
I was two 4-o's deep last night man was I on one.
by B-dub (refers to my age) November 16, 2005
 
2.
4-O
A bottle of malt liquor or beer that contains 40 ounces.
Yo, I got cock-eyed of two and a 1/2 4-O's and wrecked my 87 Dodge.
by Jonny Fromundah December 29, 2002