The term "day before yesterday" refers to the day that happened two days ago. However, there are several other phrases and terms that can be used as synonyms for this phrase. Some of the common synonyms for the phrase "day before yesterday" include "a couple of days ago," "two days back," "the day prior to yesterday," "two days ago," "yesterday eve," and "the twelfth hour." These synonyms can be used interchangeably to avoid repetition or to add variety to one's writing or speech. It's always great to have a repertoire of synonyms when expressing oneself.