The ethical theory that answers all questions of what to do, what to admire, or how to live, in terms of maximizing *utility* or happiness.
The ethical theory, advance by Bentham, J.S. Mill, and Sidgwick (and many others), that answers all questions of what to do, what to admire, or how to live, in terms of maximizing utility or happiness.
As well as ethical theory, utilitarianism is, in effect, the view of life presupposed in most modern political and economic planning, when it is supposed that happiness is measured in economic terms.
In J.S. Mill's statement of the doctrine, "actions are right in proportion as they tend to promote happiness, wrong as they tend to produce the opposite the reverse of happiness". Different conceptions of happiness separate Mill's version.
The doctrine that applies utilitarianism to actions directly is known as act utilitarianism. Indirect versions apply to such things as institutions, systems of rules of conduct, or human characteristics.
[Source : Oxford Dictionary of Philosophy]
Sometimes this is used as a synonym for the broader category of consequentialism which identifies those views that believe morality is about the maximization or minimization of some type of consequence.