Astron. a type of variable star that suddenly increases in brightness by thousands to hundreds of thousands of times up to 14 magnitudes, and then decreases in brightness over a period of months to years
See nova in American Heritage Dictionary 4
(nōˈvə)
nounpl.no·vae(-vē) or no·vas
A star that suddenly becomes much brighter and then gradually returns to its original brightness over a period of weeks to years.