Volunteer: a person who freely offers to take part in an enterprise or undertake a task. 1 u8 @9 q/ A# ^9 v5 bsynonyms: subject, participant, case, patient; informalguinea pig 6 M" K; g0 A* D# _" P7 \( Y \"each volunteer was tested three times"/ r4 n, _; }- m- D