Coadjute is a relatively obscure word, meaning to work together or cooperate closely. However, there are several synonyms that can be used interchangeably. Collaborate, conspire, and team up all convey the idea of working together towards a common goal. Another option might be to use words such as assist or aid, which imply that one party is helping the other, rather than working alongside them. Synonyms such as partner, ally, or join forces all convey a sense of unity and cooperation, making them excellent alternatives to coadjute in certain contexts. Ultimately, the choice of synonym will depend on the specific tone and emphasis desired in the given sentence or text.