A person who enters into military or other service of his own free will. In military affairs, volunteers enter into service voluntarily, but when in service they are subject to discipline and regulations like other soldiers. They sometimes serve gratuitously, but often receive a compensation.

2. Entering into service of free will; as volunteer companies.

To offer or bestow voluntarily, or without solicitation or compulsion; as, to volunteer one’s services.

To enter into any service of one’s free will, without solicitation or compulsion. He volunteered in that undertaking.