—n. 1. Also callednimbus. a geometric shape, usually in the form of a disk, circle, ring, or rayed structure, traditionally representing a radiant light around or above the head of a divine or sacred personage, an ancient or medieval monarch, etc.
2. an atmosphere or quality of glory, majesty, sanctity, or the like: the halo around Shakespeare's works; She put a halo around her son. 3. Meteorol.any of a variety of bright circles or arcs centered on the sun or moon, caused by the refraction or reflection of light by ice crystals suspended in the earth's atmosphere and exhibiting prismatic coloration ranging from red inside to blue outside (distinguished from corona).
4. Astron.a spherical cloud of gas clusters and stars that form part of a spiral galaxy.
5. an undesirable bright or dark ring surrounding an image on the fluorescent screen of a television tube, due to some fault either in transmission or reception.
—v.t. to surround with a halo.
—v.i. to form a halo.
a combining form meaning “salt,” used in the formation of compound words (halophyte); sometimes specialized as a combining form of halogen (halothane). Also,esp. before a vowel,hal-.