lightning

A single streak of lightning can be called a lightning bolt or just a bolt. Since thunder and lightning typically go together, this is sometimes called a thunderbolt or even a thunderstroke.

The bright light released is sometimes called a flash of lightning. The instance of lightning hitting something, like the ground or a tower, can be called a lightning strike or a lightning stroke. 

Thunderstorms are sometimes called lightning storms, especially when they produce a lot of lightning. Another term for this is an electrical storm. 

Some people use the term heat lightning to refer to distant lightning, typically the far-off kind that lights up the clouds on the horizon without any visible bolts or audible thunder. It’s sometimes called summer lightning. The term sheet lightning can be used to refer to this or to lightning that appears to light up the whole sky, typically due to reflection or being inside a cloud.

A rare form of lightning that appears as a glowing orb is called ball lightning. 

Technically speaking, lightning is an electrical discharge—inside a cloud, between clouds, or between clouds and the ground. When lightning strikes a cloud or the ground, it can produce a second bolt that travels in the opposite direction, called reverse lightning or a return stroke.

The adjectives fulminous and fulgurous can be used to describe things involving or relating to lightning, but they are quite formal and uncommon.

The word lightning is also commonly used in a figurative way to describe things that are very fast, as in lightning speed.