Government by violent gangs, or by the masses.

(idiomatic) A fundamental rule or principle. / (ethics) The principle that one should treat other people in the manner in which one would want to be treated by them.

(physics) the rule which states that the number of degrees of freedom in a system at equilibrium equals the number of components minus the number of phases plus 2

(law) The rule stating that an unborn child, if subsequently born alive, is considered as already in existence whenever it is to its own advantage.

(computing, of a computing language, or expert system) based on a series of simple "if then" rules

(sports) A rule that ends a one-sided contest prior to its natural conclusion.

(physics) Any of several general rules concerning the transitions between the states of a quantum mechanical system; they derive from the symmetry properties of the states and of their interactions

Alternative form of McNaughton rules

A general guideline, rather than a strict rule; an approximate measure or means of reckoning based on experience or common knowledge. / (attributive, usually hyphenated) Approximated, guesstimated.

Rule of a group of people by their own leaders as opposed to rule imposed by a foreign government or people.