volunteer
noun
[ ˌvɒlənˈtɪə ]
• a person who freely offers to take part in an enterprise or undertake a task.
• "a call for volunteers to act as foster-parents"
• a person who works for an organization without being paid.
• "the railway is operated solely by volunteers"
volunteer
verb
• freely offer to do something.
• "140 employees volunteered for redundancy"
• work for an organization without being paid.
• "volunteering is an easy way to get involved in practical conservation"
Similar:
offer one's services,
present oneself,
step forward,
come forward,
make oneself available,
Opposite:
be conscripted,
Origin:
late 16th century (as a noun, with military reference): from French volontaire ‘voluntary’. The change in the ending was due to association with -eer.