Coordinated or concerted effort by a group of people; (now usually) an instance or result of this; something achieved through the efforts of a number people, and for which credit should be shared.
Origin
Early 20th century.
Definition of group effort in US English:
group effort
noun
Coordinated or concerted effort by a group of people; (now usually) an instance or result of this; something achieved through the efforts of a number people, and for which credit should be shared.