When your shocked or surprised, or just dang interested.
Person 1: Im pregnant
Person 2: o
Person 1: Wanna see my new art?
Person 2: o?
Certainly not the invention of an illegitimate egg.
A: o
I.E.: thats my line!
A: no it's not.
girl1: say the alphabet for me
girl2: abcdefghijklmnopqrstuvwxyz...
girl1: no wtfok it's abcdefo!!
Ounce, usually of weed; about 28 grams
I just bought an o, wanna have a smoke sesh?