Volunteer: a person who freely offers to take part in an enterprise or undertake a task.- K0 Y T: k) ]& |* U
synonyms: subject, participant, case, patient; informalguinea pig- @- A1 w$ v1 h" g( s: E
"each volunteer was tested three times" 9 W& `, q6 e, J8 I) _( h8 D* }