volunteer Noun One who enters into, or offers for, any service of his/her own free will, especially when done without pay.
volunteer Noun One who enters into military service voluntarily, but who, when in service, is subject to discipline and regulations like other soldiers; -- opposed to conscript; specifically, a voluntary member of the organized militia of a country as distinguished from the standing army.
volunteer Noun A person who acts out of his own will without a legal obligation, such as a donor.
volunteer Noun A plant that grows in disturbed soil.
volunteer Noun A native or resident of the American state of Tennessee.
volunteer Verb To enlist oneself as a volunteer.
volunteer Verb To do or offer to do something voluntarily.
volunteer Verb To grow without human sowing or intentional cultivation.