volunteer

Etymology

Borrowed from Middle French voluntaire, from Latin voluntārius (“willing, voluntary”); or from voluntary + -eer.

noun

1. One who enters into, or offers themself for, any service of their own free will, especially when done without pay.
   The volunteers at the nature reserve meet up ever other Sunday to help its upkeep.
2. (military) One who enters into military service voluntarily (but who, when in service, is subject to discipline and regulations like other soldiers), as opposed to a conscript.
3. (military) A voluntary member of the organized militia of a country, as distinguished from a regular or member of the standing army.
   That summer and fall the Army organized twenty-five regiments of volunteers, including two black regiments, which would have all-black captains and lieutenants. All officers were to be selected from regulars and volunteers who had distinguished themselves[…] 2007-04-30, Edward M. Coffman, The Regulars: The American Army, 1898-1941, Harvard University Press, page 16
4. (law) A person who acts out of their own will without a legal obligation, such as a donor.
5. (botany, agriculture) A plant that grows spontaneously, without being cultivated on purpose; see volunteer plant in Wikipedia.
6. A native or resident of the American state of Tennessee.

verb

1. (intransitive) To enlist oneself as a volunteer.
2. (transitive, intransitive) To do or offer to do something voluntarily.
   to volunteer for doing the dishes
   Miranda: No good. Both routes are blocked. See these doors? The only way past is to get someone to open them from the other side. Shepard: It's not a fortress; there's got to be something. Here, maybe we can send someone in through this ventilation shaft. Jacob: Practically a suicide mission. I volunteer. Miranda: I appreciate the thought, Jacob, but you couldn't shut down the security systems in time. We need to send a tech expert. 2010, BioWare, Mass Effect 2 (Science Fiction), Redwood City: Electronic Arts, →OCLC, PC, scene: Normandy SR-2
3. (transitive) To offer, usually unprompted.
   to volunteer an explanation
4. (transitive, informal) To offer the services of (someone else) to do something.
   My sister volunteered me to do the dishes.
5. (intransitive, botany) To grow without human sowing or intentional cultivation.