The term pluperfect is a grammatical tense used to refer to an action that happened before another past action. It is also known as the past perfect tense and is formed by using the auxiliary verb 'had' plus the past participle of the main verb. The crossword solution UTTER is a verb meaning to express or state something definitely or emphatically. Therefore, the term pluperfect can be defined as a grammatical tense used to express an action that happened before another past action emphatically.