Something to write home about is a phrase used to describe something that is impressive or worth boasting about. However, if you want to express the opposite meaning, there are several antonyms that you can use. For instance, you can use words such as mediocre, unremarkable, unsatisfactory, or insignificant. These words denote something average or below average and do not elicit any excitement or enthusiasm. Another antonym of something to write home about is disappointing, which suggests that the experience or thing did not live up to expectations. All in all, there are many antonyms for something to write home about, and they all express the opposite meaning; that is, something is not noteworthy or impressive.