Volunteer: a person who freely offers to take part in an enterprise or undertake a task.7 ]( G; o1 d- A9 ?( X( `$ P
synonyms: subject, participant, case, patient; informalguinea pig 0 ~4 v- J" Z0 c( j9 Y' ?"each volunteer was tested three times" # J1 |- {- ~% v& N* R- e