As the meditation above indicates, for the human person, it means attaining a state of development such that one has "all the proper characteristics" of maturity, "lacking in no essential detail; fully developed: synonyms being "complete" or "whole" (Webster's Third International Dictionary, Unabridged).
But for the Bible of 66 books given by special revelation from God and set down under Spiritual guidance of its various writers, it does mean that its excellence of comprehensive completeness is such that adding anything to it or diminishing it in any way is condemned by its Author and Administrator.
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