Source : Webster's Revised Unabridged Dictionary (1913)

Cenozoic \Ce`no*zo"ic\, a. [Gr. ? recent + ? life.] (Geol.)
   Belonging to the most recent division of geological time,
   including the tertiary, or Age of mammals, and the
   Quaternary, or Age of man. [Written also {c[ae]nozoic},
   {cainozoic}, {kainozoic}.] See {Geology}.

   Note: This word is used by many authors as synonymous with
         Tertiary, the Quaternary Age not being included.

Source : WordNet®

Cenozoic
     n : approximately the last 63 million years [syn: {Cenozoic era},
          {Age of Mammals}]