A firefly.

Something incredibly fast (now mainly used in comparison: like or faster than greased lightning).

A device that provides an alarm to inform its user(s) that lightning has occurred nearby. Specific devices are available for a variety of applications.

A broad flash of lightning, with no visible bolt, due to reflection.

Cloud-to-ground lightning; lightning which connects (attaches) to the ground; lightning which results in the discharge of electricity between a cloud and the ground.

A metallic conductor that is attached to a high point of a building and leads to the ground to protect the building from damage by lightning.

A metallic conductor that is attached to a high point of a building and leads to the ground and protects the building from damage by lightning.

A thunderstorm.

(offensive) Supposed cause of a fire which is in fact deliberately lit by the property owner in order to benefit from insurance or similar such as destruction of documents.

(idiomatic) A difficult or challenging feat, particularly to attempt such a feat. / (idiomatic) Great, unlikely, fleeting success, particularly entrepreneurial or in the media.