"Wet squib" is a colloquial expression used to describe something that fails to meet expectations in a disappointing or underwhelming way. Some synonyms that come to mind include dud, flop, loser, letdown, disappointment, and anticlimax. Another way to describe a wet squib would be to say it fell flat, fizzled, or failed to ignite. Additionally, if something is hyped up but fails to deliver, it could be described as overhyped, overrated, or sensationalized. In any case, the term "wet squib" implies a lackluster result, and there are many words that can be used to convey the same meaning.