COLLABORATION or ART COLLECTIVE

Two or more artists who work together to produce artworks. Many artists reacting against the art market's emphasis on the individual artist as "master" sought to create work which could be ascribed not just to one artist, but rather to the collective. Members of the Guerrilla Girls, a collective of women artists working against sexism in art institutions, never appear publicly without wearing gorilla masks to protect their anonymity.

from The Bullfinch Pocket Dictionary of Art Terms Third Revised Edition
2001