Libertarian \Lib`er*ta"ri*an\ (-t[=a]"r[i^]*an), a. [See Liberty.] Pertaining to liberty, or to the doctrine of free will, as opposed to the doctrine of necessity.
Source: Webster's Revised Unabridged Dictionary (1913)
Libertarian \Lib`er*ta"ri*an\, n. One who holds to the doctrine of free will.