I think there is a wide disparity between Protestants and Catholics and between Protestants and Protestants for that matter regarding this term. So let’s discuss it.
Some say that Biblical means that it has to be exactly, explicitly in the Bible or they won’t believe it. Yet if this were true then Jesus, who pointed to the three days he was to spend in the grave was violating this definition. For there is nowhere in the Old Testament where it says that he was to spend three days in the earth explicitly. The verse Jesus sites is “just as Jonah spent three days in the belly of the whale, so the son of Man will spend three days in the grave.”
CAtholics of course say that many things are implicit in scripture. I have not found any Catholic doctrine that is not at least implicit in scripture. Further I think much of what the Protestants who require explicitness is really only implicit at best.
Some use 1 Cor 4:6 “do not go beyon what is written” to say that it has to be explicit in scripture. Well, I’ll try not to color the discussion too much on this and let’s just go for it.