voluntary

英 ['vɒlənt(ə)rɪ] 美['vɑləntɛri]

• adj. 自愿的；志愿的；自发的；故意的
• n. 志愿者；自愿行动

1. (military) a person who freely enlists for service

2. composition (often improvised) for a solo instrument (especially solo organ) and not a regular part of a service or performance