Ochlocracy (Greek: οχλοκρατία or okhlokratía; Latin: ochlocratia) is government by mob or a mass of people, or the intimidation of constitutional authorities. In English, the word mobocracy is sometimes used as a synonym. As a pejorative for majoritarianism, it's akin to the Latin phrase mobile vulgus meaning "the easily moveable crowd," from which the term "mob" originally derives.
As a term in civics it implies that there is no formal authority whatsoever, not even a commonly-accepted view of anarchism, and so disputes are raised, contended and closed by brute force − might makes right, but only in a very local and temporary way, as another mob or another mood might just as easily sway a decision. It is often associated with demagoguery and the rule of passion over reason.
The term appears to have been coined by Polybius in his Histories (6.4.6). He uses it to name the 'pathological' version of popular rule in opposition to the 'good' version, which he refers to as democracy. There are numerous mentions of the word "ochlos" in the Talmud (where "ochlos" refers to anything from "mob," "populace" to "armed guard"), as well as in Rashi, a Jewish commentary on the Bible. The word is recorded in English since 1584, derived from the French ochlocratie (1568), which stems from the original Greek okhlokratia, from okhlos "mob" and kratos "rule, power, strength"
In ancient Greek political thought ochlocracy was considered as one of the three "bad" forms of government (tyranny, oligarchy and ochlocracy) as opposed to the three "good" forms of government (monarchy, aristocracy and democracy). The distinction between "good" and "bad" was made according to whether the government form would act in the interest of the whole community ("good") or special interests ("bad").
An ochlocrat is one who is an advocate or partisan of ochlocracy. It can also used as an adjective (ochlocratic or ochlocratical).
Whether or not the decisions enforced by a mob are good or bad is another matter entirely. The threat of mob rule (not unlike the term tyranny of the majority) is often invoked -often rhetorically- against a democracy by those who oppose its majoritary decisions, sometimes fearing oppression of the needs or freedoms of minorities if democratic government is not efficiently restrained by protections given to individuals under the rule of law, sometimes concerned that demagogery may manipulate the mob and force popular currents of thought onto minority groups without respect for their or the individual's rights. There are also some who wish to see more power assigned to a certain ruling minority.
A mob, however massive, and regardless of claims to speak for 'the people', may or may not be representative of the (often silent) majority in a large society (which usually practices indirect democracy). It may be composed of a specific segment of the population interested in a specific issue, and drawn from a limited geographical space or it may be a representative popular majority.
Lapses in this control often led to loss of power, or even the loss of heads, of officials − most notably in the reign of Commodus when Cleander unwisely used the Praetorian Guard against a mob which had come to call for his head. As Edward Gibbon relates it,
The modern theories of civil disobedience and satyagraha bear some resemblance to mob rule and its mechanics. Certainly it is quite frightening for large numbers of people, even peaceful ones, to be marching and shouting common demands, if one is charged with the uncomfortable task of refusing them. If Roman guards, facing crucifixion for disobedience, could be swayed by mobs, it is obviously possible also to sway modern police even in a police state. The 1986 EDSA Revolution in the Philippines, the Velvet Revolution in former Czechoslovakia, and the resistance to the attempted military coup in the Soviet Union in 1991 that led to the collapse of that state, are situations where it is possible that it was the "mob" which won the day due to defections by authority.
Whether by intent or by circumstance, non-violent well-organized assemblies often degrade into unruly mobs. Provocation from within (such as an agent provocateur) and from external forces is often a factor, but crowd dynamics often spontaneously emerge to confront the peaceful intentions of those who rallied a crowd. Published treatises on civil disobedience theory almost always encourage practitioners to establish order within their ranks, but civil disobedience groups often face difficulty in controlling those they recruit. Dr. Martin Luther King, Jr., a renowned advocate of orderly demonstrations of group power, was assassinated after he returned to Memphis to restore order to demonstrations he had inspired but which had turned violent on his previous visit.
In certain places with a dubious record of representative democracy, physical control of polling stations is a form of mob rule that determines who wins: whoever can bring out more supporters to keep the opposing political party out, wins. Political privacy is very often nonexistent in this kind of condition, so retribution against defectors is easy.