Meaning of “the pluperfect” - Learner’s Dictionary

the pluperfect

noun us uk /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)