Other forms: choruses; chorused; chorussed; chorusing; chorussing
A chorus is a group of singers or that catchy part of a song that repeats several times.
In ancient Greek tragedies, a khoros was a group of people that spoke in unison about the actions of the characters. And that's where we got the word chorus, which usually refers to a group of singers or performers, or the refrain of a song when a group of vocalists joins a soloist. A chorus of groans may follow a teacher's announcement of an upcoming test, which means that the entire class voices its dismay at the same time.