I am jumping in late, so hope I don't repeat what has already been discussed. Also I am not saying you are a fundamentalist, rather just answering the question.
I think there are various aspects to being a fundamentalist,
- the extent to which Bible statements are taken literally
- believing only you have the truth.
I consider point 2 more dangerous, where a fundamentalist is someone that thinks their view of some Holy Book is the only correct viewpoint. This is what leads to extremism, as a person can end up justifying any behaviour once they believe they alone are worshipping God acceptably. For example, war, terrorism, shunning, refusing medical treatment.
A global flood has NOT been conclusively proven to have not happened.
Actually a global flood has been conclusively proven to not have happened, from many, many different angles. However, believing in a global flood does not make you a fundamentalist, even if your belief is wrong. You could change your mind tomorrow about the flood and still be a fundamentalist. It is more in regards to the the extent of the Bible that is taken literally and how you apply it. JWs are fundamentalists because they apply much prophecy just to themselves, and create extensive rules based on selected portions of the Bible. Other fundie groups do the same, but end up different, because they choose different prophecies and create different rules. This is possible because the Bible is so extensive and the teachings vary greatly over time, so that each group can differ in which parts to accept and which to reject, which to say are figurative and which are literal.