The Collaborative International Dictionary of English v.0.48:

capitation \cap`i*ta"tion\ (k[a^]p`[i^]*t[=a]"sh[u^]n), n. [L.
   capitatio a poll tax, fr. caput head; cf. F. capitation.]
   1. A numbering of heads or individuals. [Obs.] --Sir T.
      Browne.
      [1913 Webster]

   2. A tax upon each head or person, without reference to
      property; a poll tax.
      [1913 Webster]

WordNet (r) 3.0 (2006):

capitation
    n 1: a tax levied on the basis of a fixed amount per person