understudy UK /ˈʌndəstʌdi/US /ˈʌndɚstʌdi/verb 3noun 1forms 3 verb3 •To study or know a role to such an extent as to be able to replace the normal performer when required. •To act as an understudy (to someone). •To act in a similar manner to some known person.That lean gentleman had apparently understudied Pharaoh of old and hardened his heart. — 1935 noun1 •A performer who understudies; a standby for a study. formsunderstudied · understudying · understudies