in art, a circle of light surrounding the head or placed over it, in depictions of Christ or the saints

something resembling this

a halo of blond curls

the aura of glory or veneration surrounding an idealized person or thing

European writers … pass before our imaginations like superior beings … surrounded by a halo of literary glory — Washington Irving

a circle of light appearing to surround the sun or moon and resulting from refraction or reflection of light by ice particles in the earth's atmosphere

any appearance resembling this

the blurred haloes of the gas-lamps — Conan Doyle