1. A variable star that exhibits sudden outbursts generally arising either from the release of gravitational energy through accretion or from thermonuclear processes. The latter may occur on the surface or in the interior. The group includes many different types of variable, most of which are close binaries undergoing mass transfer. All supernovae, including those believed to consist of single stars, also come into this category. See dwarf nova; nova; nova-like variable; supernova; symbiotic star.

2. Another name for a cataclysmic binary.