The phrase "on and off" refers to something that happens intermittently, sporadically, or irregularly. There are many synonyms for this phrase, including "intermittently," "sporadically," "occasionally," "infrequently," "randomly," "erratically," "inconsistently," "from time to time," and "off and on." Each of these words conveys the same idea that something is happening or occurring in a manner that is not consistent. These synonyms can be used interchangeably depending on the context and the tone of the sentence to provide variety and interest to the writing. Overall, the use of synonyms can help to add depth and nuance to our language.