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n. pl. ha·los or ha·loes
a. A luminous ring or disk of light surrounding the heads or bodies of sacred figures, such as saints, in religious paintings; a nimbus.
b. A ring or disk resembling the halo of a sacred figure: "She had a halo of red hair floating over a delicate ivory face" (Judith Ortiz Cofer).
c. A feeling of glory, reverence, or admiration associated with a person or thing: "By the 1930s, insulin's halo had begun to tarnish, for it became clear that patients who had the illness ... were prone to problems of the small blood vessel" (James S. Hirsch).
a. A circular band of colored light around a light source, as around the sun or moon, caused by the refraction and reflection of light by ice particles suspended in the intervening atmosphere.
b. A roughly spherical region of relatively dust-free space surrounding a galaxy and extending beyond the visible parts of the galaxy. Galactic halos contain stars (often located in globular clusters), gas, and dark matter.
tr.v. ha·loed, ha·lo·ing, ha·loes
To encircle with a halo.

[Medieval Latin halō, from accusative of Latin halōs, from Greek, threshing floor, disk of or around the sun or moon.]