An optically violent variable quasar (often abbreviated as OVV quasar) is a type of highly variable quasar

Quasar

A quasi-stellar radio source is a very energetic and distant active galactic nucleus. Quasars are extremely luminous and were first identified as being high redshift sources of electromagnetic energy, including radio waves and visible light, that were point-like, similar to stars, rather than...

. It is a subtype of blazar

Blazar

A blazar is a very compact quasar associated with a presumed supermassive black hole at the center of an active, giant elliptical galaxy...

 that consists of a few rare, bright radio galaxies, whose visible light output can change by 50% in a day. They are similar in appearance to BL Lac

BL Lac object

A BL Lacertae object or BL Lac object is a type of active galaxy with an active galactic nucleus and is named after its prototype, BL Lacertae. In contrast to other types of active galactic nuclei, BL Lacs are characterized by rapid and large-amplitude flux variability and significant optical...

s but generally have a stronger broad emission line, and tend to have higher red shift

Red shift

-Science:* Redshift, the increase of wavelength of detected electromagnetic radiation with respect to the original wavelength of the emission* Red shift, an informal term for a bathochromic shift...

components.