Definitionen
1.NounOne who enters into, or offers themselves 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.NounOne 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.NounA voluntary member of the organized militia of a country, as distinguished from a regular or member of the standing army.
4.NounA person who acts out of their own will without a legal obligation, such as a donor.
5.NounA plant that grows spontaneously, without being cultivated on purpose; see volunteer plant in Wikipedia.
6.NounA native or resident of the American state of Tennessee.
7.VerbTo enlist oneself as a volunteer.
8.VerbTo do or offer to do something voluntarily."to volunteer for doing the dishes"
9.VerbTo offer, usually unprompted."to volunteer an explanation"
10.VerbTo offer the services of (someone else) to do something."My sister volunteered me to do the dishes."
11.VerbTo grow without human sowing or intentional cultivation.