I. ˈ ̷ ̷ ̷ ̷ˌ ̷ ̷ ̷ ̷ verb
Etymology: under (I) + study
intransitive verb
: to study another actor's part in order to be his substitute in an emergency
transitive verb
1. : to study (a part or character) as understudy : prepare as understudy to (an actor)
2. : to learn (as a job or procedure) thoroughly by observation or apprenticeship
understudy a banking operation
II. noun
: one who stands prepared to act another's part or take over the work or duties of another