Liberality, which since C14 had carried the sense of generosity, and later of open-mindedness, was joined by political Liberalism from eC19. Libertarian in 1C18 indicated a believer in free will as againstdeterminism (cf. DETERMINE), but from 1C19 acquired social and political senses, sometimes close to liberal.It is especially common in mC20 in libertarian socialism, which is not liberalism but a form ofSOCIALISM (q.v.) opposed to centralized andBUREAUCRATIC (q.v.) controls.
In the established party-political sense, Liberal is now clear enough. But liberal as a term of political discourse is complex. It has been under regular and heavy attack from conservative positions, where the senses of lack of restraint and lack of discipline have been brought to bear, and also the sense of a (weak and sentimental) generosity. The sense of a lack of rigour has also been drawn on in intellectual disputes. Against this kind of attack, liberal has often been a group term for PROGRESSIVE or RADICAL (qq.v.) opinions, and is still clear in this sense, notably in USA. Butliberal as a pejorative term has also been widely used by socialists and especially Marxists. This use shares the conservative sense of lack of rigour and of weak and sentimental beliefs. Thus far it is interpreted byliberals as a familiar complaint, and there is a special edge in their reply to socialists, that they are concerned with political freedom and that socialists are not. But this masks the most serious sense of the socialist use, which is the historically accurate observation thatliberalism is a doctrine based on INDIVIDUALIST (q.v.) theories of man and society and is thus in fundamental conflict not only with SOCIALIST (q.v.) but with most strictly SOCIAL (q.v.) theories. The further observation, that liberalism is the highest form of thought developed within BOURGEOIS (q.v.) society and in terms of CAPITALISM (q.v.), is also relevant, for when liberal is not being used as a loose swear-word, it is to this mixture of liberating and limiting ideas that it is intended to refer. Liberalism is then a doctrine of certain necessary kinds of freedom but also, and essentially, a doctrine of possessive individualism.
of course we could just link to the OED or mirriam-webster because they really are great when it comes to political definitions, much like wikipedia and your ole fave google