Suppositive is an adjective that refers to something that is assumed or believed to be true without definite proof. Some synonyms for this word that help to convey the same sentiment include presumptive, conjectural, hypothetical, speculative, putative, and supposed. These words are often used to describe situations where there is some uncertainty about the truth of a certain proposition. For example, a legal argument may be based on suppositive evidence that is reasonably believed to be true even though it has not been definitively proven. In everyday conversation, these words can be used to express a certain level of uncertainty or speculation about a given topic.