Wikipedia
Leaderless resistance, or phantom cell structure, is a social resistance strategy in which small, independent groups ( covert cells), including individuals (a solo cell called a " Lone Wolf"), challenge an established institution such as a law, economic system, social order, government, et cetera. Leaderless resistance can encompass anything from non-violent protest and civil disobedience to vandalism, terrorism and other violent activity. Leaderless cells lack bidirectional, vertical command links and operate without hierarchal command. While it lacks a central command, the concept includes a common goal between the individual actor and the group or social movement from which the ideology was learned.
Given the simplicity of the strategy, as well as the fact that it is difficult to stamp out, leaderless resistance has been employed by a wide range of movements, including animal-liberation, radical environmentalist, anti-abortion activist, military invasion resistance, colonialism resistance, terrorist, and hate groups.