Doubtable
Doubtable adjective - Giving good reason for being doubted, questioned, or challenged.
Usage example: her argument rested entirely upon some highly doubtable logic
Open and doubtable are semantically related. in questionable topic. In some cases you can use "Open" instead an adjective "Doubtable", when it comes to topics like doubtful.
Cite this Source
Open and Doubtable. (2016). Retrieved 2026, August 15, from https://thesaurus.plus/related/doubtable/open
Doubtable & Open. N.p., 2016. Web. 15 Aug. 2026. <https://thesaurus.plus/related/doubtable/open>.
Open or Doubtable. 2016. Accessed August 15, 2026. https://thesaurus.plus/related/doubtable/open.
Google Ngram Viewer shows how "doubtable" and "open" have occurred on timeline