There are several synonyms for the phrase "cleave together," all of which describe the act of becoming unified or joined together. Some common synonyms include adhere, cling, stick, and coalesce. These words all express a sense of sticking or merging together in a way that creates a single entity. Additionally, the phrase "bond together" is another common synonym for "cleave together," which can imply a strong emotional connection or sense of solidarity. Whether used in a literal or figurative context, all of these words convey the idea of things coming together to form a stronger, more unified whole.