Meaning of “the pluperfect” - Learner’s Dictionary

the pluperfect

noun uk us /ˌpluːˈpɜːfɪkt/ (also the past perfect)

the form of the verb that is used to show that an action had already finished when another action happened. In English, the pluperfect is made with 'had' and a past participle.

(Definition of “the pluperfect” from the Cambridge Learner’s Dictionary © Cambridge University Press)