The Collaborative International Dictionary of English v.0.48:

Anthelion \Ant*hel"ion\ (?; 277, 106), n.; pl. Anthelia.
   [Pref. anti + Gr. ? sun.] (Meteor.)
   A halo opposite the sun, consisting of a colored ring or
   rings around the shadow of the spectator's own head, as
   projected on a cloud or on an opposite fog bank.
   [1913 Webster]