fogbow

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A faint white or yellowish arc-shaped light, similar to a rainbow, that sometimes appears in fog opposite the sun. Also called seadog.

Century Dictionary and Cyclopedia

1. n. A faintish white arch seen in fog, similar to the rainbow, and due to the action of the same causes, the globules of water of the fog playing the same part as the raindrops. It is, however, usually less extended and less sharply defined, and if colored at all has only a slightly rosy tint. Fog-bows are sometimes observed at sea when the fog is very dense, as off the coast of Newfoundland.

Wiktionary

1. n. A white arc or circle, similar to a rainbow, which can appear in the sky in foggy conditions as sunlight passes through small airborne water droplets.

GNU Webster's 1913

1. n. A nebulous arch, or bow, of white or yellowish light sometimes seen in fog, etc.