exact meaning of "arguably"

[kjc0123]

What is the exact meaning of "arguably" in the following sentences?

The Catholic Inquisition published the book that arguably could be called the most blood-soaked publication in human history. Malleus Maleficarum�or The Witches' Hammer�indoctrinated the world to "the dangers of freethinking women" and instructed the clergy how to locate, torture, and destroy them.

[Quizmonster]

'Arguably' means 'a case can be made for making such a claim'. In other words, one is saying that this thing - whatever it is - is quite possibly true. So, a film might be called "arguably the most violent film ever made" or a meal might be described as "arguably the finest meal I have ever eaten". The idea is that you can "argue the case" in favour of the claim.

[jno]

It's what people say these days when they mean 'perhaps'. In the sentence you quote, it's unnecessary, because 'could' also means 'perhaps'.