What is "superbubble"

n. (context astronomy English) A very large region of space, relatively free of matter, created by multiple supernova explosions

A superbubble or supershell is a cavity which is hundreds of light years across, and is filled with 10 K gas blown into the interstellar medium by multiple supernovae and stellar winds. The Solar System lies near the center of an old superbubble, known as the Local Bubble, whose boundaries can be traced by a sudden rise in dust extinction of stars at distances greater than a few hundred light years.