The phrase "tacit agreement" refers to an agreement that is implied or understood without being explicitly stated. There are several synonyms that can be used to convey a similar meaning, such as "implicit agreement," "unspoken understanding," "implied consent," "mutual understanding," and "silent concurrence." Each of these phrases suggests an agreement that is not explicitly verbalized or written down, but instead is understood through actions or nonverbal communication. These synonyms can be useful in a variety of contexts, such as in business negotiations, where some agreements may be implied but not explicitly stated in a contract.