halo

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. 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.
2. n. Something resembling this band.
3. n. A luminous ring or disk of light surrounding the heads or bodies of sacred figures, such as saints, in religious paintings; a nimbus.
4. n. The aura of majesty or glory surrounding a person or thing that is regarded with reverence, awe, or sentiment.
5. v. To encircle with or as if with a halo.

Century Dictionary and Cyclopedia

1. n. A luminous circle, either white or colored, seen round the sun or moon, and commonly of 22° or of 46° radius, the definite radii depending on the definite angles of ice-crystals. Sometimes one of these only is seen, and sometimes both appear at the same time. Halos are due to the refraction of light as it passes through minute ice-needles in the atmosphere. They are frequently accompanied by supernumerary circles, parhelia or mock suns, paraselenæ or mock moons, and variously arranged white bands, crosses, or arcs. All of these phenomena are the result of the refraction, reflection, and diffraction of light when it falls upon crystals of ice suspended in the atmosphere. Halos and their attendant phenomena are more frequent in winter than in summer, and are more commonly observed in the arctic regions than in warmer climates.
2. n. A circle of light, as the nimbus surrounding the head of a saint. See nimbus.
3. n. A brownish circle round the nipple; an areola.
4. n. Pl. halones (hal′ ō˙-nēz). In ornithology, certain chiefly concentric rings of color in the yolk of an egg: an optical appearance due to the deposition of the yolk in successive layers or strata.
5. n. Figuratively, an ideal glow or glory investing an object as viewed through the medium of feeling or sentiment.
6. To form a halo.
7. To surround with a halo.

Wiktionary

1. n. astronomy A circular band of coloured light, visible around the sun or moon etc., caused by reflection and refraction of light by ice crystals in the atmosphere.
2. n. astronomy A cloud of gas and other matter surrounding and captured by the gravitational field of a large diffuse astronomical object, such as a galaxy or cluster of galaxies.
3. n. Anything resembling this band, such as an effect caused by imperfect developing of photographs.
4. n. religion nimbus, a luminous disc, often of gold, around or over the heads of saints, etc., in religious paintings.
5. n. The metaphorical aura of glory, veneration or sentiment which surrounds an idealized entity.
6. v. transitive To encircle with a halo.

GNU Webster's 1913

1. n. A luminous circle, usually prismatically colored, round the sun or moon, and supposed to be caused by the refraction of light through crystals of ice in the atmosphere. Connected with halos there are often white bands, crosses, or arches, resulting from the same atmospheric conditions.
2. n. A circle of light; especially, the bright ring represented in painting as surrounding the heads of saints and other holy persons; a glory; a nimbus.
3. n. An ideal glory investing, or affecting one's perception of, an object.
4. n. A colored circle around a nipple; an areola.
5. v. To form, or surround with, a halo; to encircle with, or as with, a halo.

WordNet 3.0

1. n. a toroidal shape
2. n. a circle of light around the sun or moon
3. n. an indication of radiant light drawn around the head of a saint