The Collaborative International Dictionary of English v.0.48:

Census \Cen"sus\, n. [L. census, fr. censere. See Censor.]
   1. (Bot. Antiq.) A numbering of the people, and valuation of
      their estate, for the purpose of imposing taxes, etc.; --
      usually made once in five years.
      [1913 Webster]

   2. An official registration of the number of the people, the
      value of their estates, and other general statistics of a
      country.
      [1913 Webster]

   Note: A general census of the United States was first taken
         in 1790, and one has been taken at the end of every ten
         years since.
         [1913 Webster]

WordNet (r) 3.0 (2006):

census
    n 1: a periodic count of the population [syn: census, nose
         count, nosecount]
    v 1: conduct a census; "They censused the deer in the forest"