Wiktionary
double quasar
n. 1 (context galaxy English) Two quasars which form a system, such that they gravitationally interact, or are part of the same cluster of galaxies; a binary quasar. 2 (context galaxy English) Two quasars that appear to be paired when seen in an image, either because they orbit one another (binary quasars) or happen to be in the same line of sight even though they are separated by a great distance.