The Collaborative International Dictionary of English v.0.48:

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.
   [1913 Webster]

   Note: This word is used by many authors as synonymous with
         Tertiary, the Quaternary Age not being included.
         [1913 Webster]

WordNet (r) 3.0 (2006):

Cenozoic
    adj 1: of or relating to or denoting the Cenozoic era
    n 1: approximately the last 63 million years [syn: Cenozoic,
         Cenozoic era, Age of Mammals]