Real Dictionary

halo
countable noun: A halo is a circle of light round a person or thing, or something that looks like a circle of light.
countable noun: A halo is a circle of light that is shown in pictures round the head of a holy figure such as a saint or angel.

halo in American English
a ring of light that seems to encircle the sun, moon, or other luminous body: it results from the refraction of light through ice crystals in our atmosphere
to encircle with a halo
intransitive verb: to form a halo
noun: 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
transitive verb: to surround with a halo

halo in British English
noun: a disc or ring of light around the head of an angel, saint, etc, as in painting or sculpture
verb: to surround with or form a halo

halo- in American English
of the sea
combining form: a combining form meaning “salt,” used in the formation of compound words (halophyte). It is sometimes specialized as a combining form of halogen (halothane)

halo- in British English
combining form: indicating salt or the sea