The Collaborative International Dictionary of English v.0.48:

O \O\ ([=o]), n.; pl. O's or Oes ([=o]z).
   1. The letter O, or its sound. "Mouthing out his hollow oes
      and aes." --Tennyson.
      [1913 Webster]

   2. Something shaped like the letter O; a circle or oval.
      "This wooden O [Globe Theater]". --Shak.
      [1913 Webster]

   3. A cipher; zero. [R.]
      [1913 Webster]

            Thou art an O without a figure.       --Shak.
      [1913 Webster]

V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

OES
       Olivetti EntsorgungsService (Olivetti)


V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

OES
       Open Enterprise Server (Novell, Linux)