Meaning

noun any utterance produced simultaneously by a group

noun a group of people assembled to sing together

noun the part of a song where a soloist is joined by a group of singers

originThe noun is borrowed from Medieval Latin chorus (“church choir”), Latin chorus (“group of dancers and singers; dance”), from Ancient Greek χορός (khorós, “group of dancers and singers, choir, chorus; dance accompanied by song; round dance”); The verb is derived from the noun. Doublet of choir, chore, and hora.

Etymology from Wiktionary, CC BY-SA 3.0