Source : Webster's Revised Unabridged Dictionary (1913)

Solar parallax \Solar parallax\
   The parallax of the sun, that is, the angle subtended at the
   sun by the semidiameter of the earth. It is 8.''80, and is
   the fundamental datum.

Source : WordNet®

solar parallax
     n : the angle subtended by the mean equatorial radius of the
         Earth at a distance of one astronomical unit