Presupposition A belief that takes precedence over other beliefs in such a way that without the former these other beliefs have no ground, basis, or foundation. 

Presuppositions may be classified as either weak or strong to indicate their relative strengths (weaker/stronger).  A weak presupposition is a  belief that governs other beliefs but some belief takes precedence over it.  A strong presupposition is a belief that takes governs other beliefs and nothing takes precedence over it. Beliefs exist in a chain or hierarchy. A strong presupposition is ultimate in the chain or hierarchy of beliefs.  Belief in the risen Christ speaking by the Spirit in Scripture is the ultimate presupposition in the Christian worldview.  See John Frame for these distinctions along with the added notion of "a basic commitment of the heart" (Doctrine 45, 125-26).

We should note that in apologetics presuppositions also have what might be called objective and a subject aspects.  The subjective aspects are described above.  The objective side of a presupposition emphasizes the necessary preconditions for rationality itself.  In this sense, presuppositions are "ultimates" which means "one may not 'get behind' them but they alone are what make any fact intelligible" (S. Oliphint, Consistency 23). The "ultimates" are God, His knowledge, interpretation, and control of all things, and His self-revealing speech in nature and in Scripture by Christ through the Spirit. Bahnsen stresses the subjective aspect (VTA 2n4) but does not lose sight of the objective aspect when discussing the trancendental-presuppositional argument (VTA 5n10).