LIBERTARIAN
-noun
1. a person who advocates liberty, esp. with regard to thought or conduct.
2. a person who maintains the doctrine of free will (distinguished from necessitarian).
–adj.
3. advocating liberty or conforming to principles of liberty.
4. maintaining the doctrine of free will.
N.B. The dictionary fails badly on current usage here. A libertarian is commonly used (for example, in relation to the "Libertarian Party" in the United States) to refer to a person with extreme views on the relation of the individual to the state — sometimes to society as a whole. From a libertarian perspective, all governmental taxes and regulations are suspect. Even highways and armies can fall under this proscription. Some extreme free marketers fall into this group. Yet they are far from belonging to the right-wing conservatives of today, for on social questions, they may be extremely liberal.