The Collaborative International Dictionary of English v.0.48:

White person \White person\
   A person of the Caucasian race (--6 Fed. Rep. 256).

   Note: In the time of slavery in the United States white
         person was generally construed as a person without
         admixture of colored blood. In various statutes and
         decisions in different States since 1865 white person
         is construed as in effect (as of 1913): one not having
         any negro blood (Ark., Okla.); one having less than one
         eighth of negro blood (Ala., Fla., Ga., Ind., Ky., Md.,
         Minn., Miss., Mo., N.C., S.C., Tenn., Tex.); one having
         less than one fourth (Mich., Neb., Ore., Va.); one
         having less than one half (Ohio). Since the passage of
         civil rights legislation in the 1960's and 1970's, the
         term has little legal significance -- for some
         purposes, as in filling out questionnaires, a person's
         race is whatever the person claims it to be.
         [Webster 1913 Suppl. +PJC]

WordNet (r) 3.0 (2006):

White person
    n 1: a member of the Caucasoid race [syn: White, White
         person, Caucasian]