Someone or something that disappoints or does not meet expectations. The film got a lot of hype, but I thought it was a bit of a damp squib.
a damp squibmainly BRITISH
COMMON A damp squib is something which is much less impressive or exciting than it was expected to be. As a rebellion, it was something of a damp squib. The whole campaign turned out to be a damp squib. Note: A squib is a small firework. A damp squib would not go off properly, and so it would be a disappointment.
a damp squiban unsuccessful attempt to impress; an anticlimax.
This expression stems from the idea that a squib, a type of small firework, will not have the desired explosive effect if it is damp.
a damp ˈsquib(British English, informal) an event, experience, etc. that is expected to be interesting or exciting, but is in fact boring or ordinary: In the end, the party turned out to be rather a damp squib.
A squib is a type of small firework. If it is damp, it will not burn properly.