Volunteer: a person who freely offers to take part in an enterprise or undertake a task. : m: g+ Z. O3 Hsynonyms: subject, participant, case, patient; informalguinea pig' f( A6 \" u1 n2 [, @* ^) }% R9 C
"each volunteer was tested three times" 6 k# m7 d; ^: b! d) \2 L