The phrase "nine day wonder" is used to describe something or someone that quickly gains popularity or attention before fading away just as quickly. When looking for synonyms for this term, one can use phrases such as "flash in the pan," "fleeting sensation," or "one-hit wonder." Other synonyms include "fad," "trend," "momentary craze," or "transient phenomenon." These terms all refer to something or someone that experiences a short burst of attention before being forgotten or replaced. Whether used to describe a viral video or a passing trend in fashion, these synonyms capture the essence of the "nine day wonder" concept.