Something is controvertible if it’s open to debate or can be disputed. For example, the theory that Bigfoot or the Loch Ness monster exist is controvertible, as it's being challenged all the time.
Controvertible claims or ideas allow room for disagreement. When evidence is inconclusive, people's opinions about what it means may differ, and the topic is ripe for discussion and further exploration. Certain historical events and pieces of information are considered controvertible, including the true identity of Shakespeare. Being controvertible doesn’t mean something is false; it just means it's not universally accepted as fact.