A form of cataclysmic binary, more specifically known as a U Geminorum star, that undergoes repeated outbursts. These occur when thermal instabilities trigger a sudden brightening of the accretion disk around the white-dwarf primary. The individual maxima have a general resemblance to the light-curve of a nova, although with a smaller amplitude (2–6 mag.) and a shorter duration (a few days). The intervals between outbursts are far shorter than those in a recurrent nova and, although irregular and unpredictable, show a mean cycle length for each individual star. Accretion on to the primary will probably eventually produce a nova outburst.