"The whole nine yards" is an idiom that refers to giving everything or going all out. There are several possible synonyms that can be used to convey the same meaning, depending on the context. One possible alternative is "the whole enchilada," which is a phrase that implies completeness or entirety. Another popular synonym is "the whole kit and caboodle," which has a similar connotation of comprehensiveness or totality. Other similar expressions might include "the whole shebang," "the whole ball of wax," or "the whole shooting match." Ultimately, the choice of synonym will depend on the specific situation and the speaker's preference.