volunteer

Definitions

• One who enters into, or offers for, any service of his/her own free will, especially when done without pay.
• (military) 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.
• (legal) A person who acts out of his own will without a legal obligation, such as a donor.
• (botany) A plant that grows spontaneously, without being cultivated on purpose; see in Wikipedia.
• A native or resident of the American state of Tennessee.