Lewis & Short

vŏluntārĭus, a, um, adj. [voluntas], willing, of his or its own free-will, voluntary.

  1. I. Lit.
    1. A. Adj.: milites, volunteers, Caes. B. C. 3, 91 fin.; Liv. 28, 45, 13: ferocissimus quisque juvenum, id. 1, 59, 5: auxilia, Cic. Fam. 15, 4, 3: servi, id. Rep. 1, 43, 67: procurator, id. Brut. 4, 17: est Asinius quidam, senator voluntarius, lectus ipse a se, id. Phil. 13, 13, 28.
    2. B. Subst.: vŏluntārĭi, ōrum, m. (milites), volunteers, Caes. B. G. 5, 66; Liv. 1, 30, 7; 5, 16, 5; 25, 19, 13; Capitol. M. Aur. 21; Inscr. Orell. 244 and 512.
  2. II. Transf., of things: mors, suicide, Cic. Fam. 7, 3, 3: discessus voluntarius sine ullā spe reditus, id. Att. 9, 13, 4: nam hoc ipsum ita justum est, quod recte fit, si est voluntarium, id. Off. 1, 9, 28: verbera, Just. 2, 8, 7: servitus, Tac. G. 24: deditio, id. H. 2, 45: lex, Petr. 107: accusationes, Tac. Or. 41: Junonis transitus in urbem nostram, Val. Max. 1, 8, 35: herba, growing of itself, spontaneous, Plin. 20, 22, 90, § 245.
    Adv.: vŏ-luntārĭē, voluntarily, Arn. 2, 74; Hyg. Fab. 41.