understudy

• POS: Noun, Verb (transitive)
• HYPHEN: un=der=stud=y

CIDE DICTIONARY

understudy, v. t. & i. 

 To study, as another actor's part, in order to be his substitute in an emergency; to study another actor's part.  [1913 Webster]

understudy, n. 

 One who studies another's part with a view to assuming it in an emergency.  [1913 Webster]

OXFORD DICTIONARY

understudy, n. & v. esp. Theatr.
--n. (pl. -ies) a person who studies another's role or duties in order to act at short notice in the absence of the other.
--v.tr. (-ies, -ied)
1 study (a role etc.) as an understudy.
2 act as an understudy to (a person).

THESAURUS

understudy

act for, advocate, agent, alter ego, alternate, alternative, amicus curiae, analogy, answer for, appear for, attorney, back up, backup, backup man, bit player, champion, change, change places with, changeling, commission, comparison, copy, counterfeit, crowd out, cut out, deputize, deputy, displace, double, double for, dummy, equal, equivalent, ersatz, exchange, executive officer, exponent, extra, fake, figurant, figurante, figurehead, fill in for, fill-in, front for, ghost, ghostwrite, ghostwriter, imitation, lieutenant, locum, locum tenens, makeshift, metaphor, metonymy, mute, next best thing, paranymph, personnel, phony, pinch hitter, pinch-hit, pinch-hit for, pleader, procurator, proxy, relief, relieve, replace, replacement, represent, representative, reserve, reserves, ringer, second, second in command, second string, secondary, sign, spares, speak for, spear-carrier, spell, spell off, stand in for, stand-in, standby, sub, subrogate, substituent, substitute, substitute for, substitution, succedaneum, succeed, supe, super, supernumerary, supersede, superseder, supplant, supplanter, support, supporting actor, supporting cast, surrogate, swap places with, symbol, synecdoche, third string, token, understudy for, utility man, utility player, vicar, vicar general, vice, vice-president, vice-regent, vicegerent, walk-on, walking gentleman