Light fog is a type of weather phenomenon that occurs when a thin layer of fog is illuminated by light. It is usually seen in the early morning or late evening when the sun is low in the sky and the air is still. The term 'light fog' can also be used to describe a situation where visibility is reduced due to a thin layer of fog, but not to the point of complete obscurity. The crossword solution for this term is MIST, which is a collection of tiny water droplets suspended in the air.