What is the meaning of social movement?

A social movement is a type of group action.

Definitions

a) Social movements can be defined as "organizational structures and strategies that may empower oppressed populations to mount effective challenges and resist the more powerful and advantaged elites".

b) Mario Diani argues that nearly all definitions share three criteria: "a network of informal interactions between a plurality of individuals, groups and/or organizations, engaged in a political or cultural conflict, on the basis of a shared collective identity"