WordDictionary

Adjective:

• Relating to the beliefs of libertarians, as in, "He has ''libertarian'' views". A relative tendency towards liberty, as in "''libertarian'' capitalist".

Noun:

• In the philosophy branch of metaphysics, a believer in thinking beings' freedom to choose their own destiny, i.e. a believer in Free Will as opposed to those who believe the future is predetermined.
• Europe An anarchist, typically with socialist implications.
• US A believer in a political doctrine that emphasises individual liberty and a lack of governmental regulation and oversight both in matters of the economy ('free market') and in personal behavior where no one's rights are being violated or threatened. Also 'classical liberal', akin to 'anarcho-capitalist'.
• One who advocates liberty either generally or on a specific issue, e.g. "civil libertarian" (in favour of civil liberties).
• prefixed to "Republican" a member of the Republican Party (especially a legislator) who emphasizes economic and Constitutional, rather than religious and personal, aspects of the party's platform.

Proper noun:

• politics A member of a political party or movement that uses the term "Libertarian" in its name (e.g., the Libertarian Party of the United States); one who is likely to support policies that are libertarian.