Volunteer: a person who freely offers to take part in an enterprise or undertake a task. ) ~4 }3 e. x [( s: [) V/ Wsynonyms: subject, participant, case, patient; informalguinea pig 0 _' j+ K: \' ^, A3 h. o"each volunteer was tested three times" ; D2 i! o, V/ c B5 U5 B