Co- A form of the prefix com-, signifying with, together, in conjunction, joint. It is used before vowels and some consonants. See Com-.
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  CO
       n 1: an odorless very poisonous gas that is a product of
            incomplete combustion of carbon [syn: carbon monoxide,
             carbon monoxide gas]
       2: a hard ferromagnetic silver-white bivalent or trivalent
          metallic element; a trace element in plant and animal
          nutrition [syn: cobalt, atomic number 27]
       3: one who refuses to serve in the armed forces on grounds of
          conscience [syn: conscientious objector]
       4: a state in west central United States in the Rocky Mountains
          [syn: Colorado, Centennial State]