Interposit is a relatively uncommon word that refers to something or someone that has been introduced or placed between other things or people. Though interposit may not be a commonly-used word, there are several synonyms that could be used in its place such as intermediary, mediator, go-between, liaison, or middleman. These words all refer to an individual or thing that functions as a connector or facilitator between two or more other entities. In everyday language, we often use words like these when discussing conflict resolution or negotiations, as an intermediary or mediator is often necessary to reach a fair compromise or agreement between opposing parties.