Yes, it is.
The word “Trinity” is not found in the bible. The theological concept is there (c.f. Mt. 28), but the doctrinal definitions of the relationship among the 3 persons of the Most Holy Trinity were not dogmatically defined in such a way to express and defend this orthodox doctrine from non-Trinitarian heresies until the Council of Nicea (325 AD) and the three other great early Councils (Constantinopile 381 AD; Ephesus 431 AD; and Chalcedon 451 AD, where Pope St. Leo the Great provided the most concise Christilogical definition with respect to the Divine and Human natures our Lord Jesus Christ.)
So strictly speaking, the word “Trinity” and the “Doctrinal Definition of the Trinity” are not “explicitly” stated in the Sacred Scripture. The Trinitarian Doctrine is implicit in the Biblical text, but it would take the reflections of the early Church Fathers and the great Councils to more fully develop and define this beautiful Doctrine of orthodox Christian belief.
Regards