volen-, volunt-, voli-, vol-

1. Of feelings, etc.; arising or developing in the mind without external constraint; having a purely spontaneous origin or character.
2. Of actions performed or done of one’s own free will, impulse, or choice; not constrained, prompted, or suggested by another.

1. One who willingly offers or enrolls himself/herself for military service, in contrast to those who are under obligation to do so, or who form part of a regular army or military force.
2. One who voluntarily offers his services in any capacity; one who of his own free will takes part in any enterprise or activity.
3. To offer to undertake or perform (something).

The action of serving, or offering one’s services, as a volunteer.