noun.
A bright spot sometimes appearing at either side of the sun, often on a luminous ring or halo, caused by the refraction and reflection of sunlight by ice crystals suspended in the earth's atmosphere.
The Century Dictionary and Cyclopedia
noun.
An intensification of a circular space in a solar halo, generally in prismatic colors, sometimes dazzlingly bright.
the GNU version of the Collaborative International Dictionary of English
noun.
A mock sun appearing in the form of a bright light, sometimes near the sun, and tinged with colors like the rainbow, and sometimes opposite to the sun. The latter is usually called an anthelion. Often several mock suns appear at the same time. Cf. paraselene.