- a faint discharge of blue light from the top of a thunderstorm cloud that propagates upward: extends approximately from the bottom to the top of the stratosphere and is not detectable from the ground.
- A flash of light in the sky caused by an electrical discharge from the Earth’s surface to a cloud. Reverse lightning is so called because lightning typically occurs between clouds or travels from a cloud to the Earth’s surface. Also called return stroke See note at lightning.
- A conical discharge of blue light that starts from the top of active thunderstorm clouds and proceeds upward. Blue jets can last up to several hundred milliseconds and are believed to connect the top of a thundercloud with the ionosphere.