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.
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   2. Something shaped like the letter O; a circle or oval.
      "This wooden O [Globe Theater]". --Shak.
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   3. A cipher; zero. [R.]
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            Thou art an O without a figure.       --Shak.
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	Os \Os\, n.; pl. Ossa. [L.]
   A bone.
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	Os \Os\, n.; pl. Ora. [L.]
   A mouth; an opening; an entrance.
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	Os \Os\, n.; pl. Osar. [Sw. [*a]s ridge, chain of hills, pl.
   [*a]sar.] (Geol.)
   One of the ridges of sand or gravel found in Sweden, etc.,
   supposed by some to be of marine origin, but probably formed
   by subglacial waters. The osar are similar to the kames of
   Scotland and the eschars of Ireland. See Eschar.
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	Os \Os\, n. (Chem.)
   The chemical symbol for the element osmium.
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	OS
       Operating System