/ ˈʌndəstʌdi; NAmE -dərs-/ noun , verb
■ noun
( pl. -ies ) understudy (to sb) an actor who learns the part of another actor in a play so that they can play that part if necessary
■ verb
( under·stud·ies , under·study·ing , under·stud·ied , under·stud·ied ) [ vn ] to learn a part in a play as an understudy ; to act as an understudy to sb