The word "suppositionally" means based on assumption or speculation. Some synonyms for this word could be hypothetically, theoretically, speculatively, or conjecturally. These words all convey the idea of something being considered without concrete proof or evidence to support it. Additionally, words like tentatively, provisionally, and conditionally could also be used to describe suppositional ideas or statements that are subject to change. No matter which synonym is used, it is important to recognize that suppositionally implies some level of uncertainty or doubt, and should be used carefully and thoughtfully in order to avoid misleading or misinforming others.