'Understudy' definitions:

Definition of 'understudy'

(from WordNet)
noun
An actor able to replace a regular performer when required [syn: understudy, standby]
verb
Be an understudy or alternate for a role [syn: understudy, alternate]

Definition of 'Understudy'

From: GCIDE
  • Understudy \Un"der*stud`y\, v. t. & i. (Theater) To study, as another actor's part, in order to be his substitute in an emergency; to study another actor's part. [1913 Webster]

Definition of 'Understudy'

From: GCIDE
  • Understudy \Un"der*stud`y\, n. One who studies another's part with a view to assuming it in an emergency. [1913 Webster]