Basement show

A basement show is a musical performance, often of the punk rock or hardcore punk variety, that is held in the basement of a residential home, rather than at a traditional venue. These are also sometimes referred to as "house shows" as they can happen anywhere in a residential house, not just in the basement. 
Background.
Basement shows are normally held for a variety of reasons, including:
Some bands have written songs about this, such as Deerhunter's "Basement Scene," "Theme Song for a New Brunswick Basement Show" by Lifetime and "It Sounds Better In The Basement" by The Devil Is Electric. Basement shows also build on the notion of music being more than just performance, but about the building and strengthening of community. By opening one's home to these performances where people come together to share their artwork/music, they open up a community-based cultural exchange.