From Longman Dictionary of Contemporary Englishwet blanketˌwet ˈblanket / $ ˈ. ˌ../ noun [countable] informalSPOIL someone who seems to want to spoil other people’s fun, for example by refusing to join them in something enjoyable that they are doing
Examples from the Corpus
wet blanket• Why be a wet blanket now?• Roy is just like something you'd find in a baby's pram-a wet blanket.• They thought he was a middle aged wet blanket.• But there was no large wet blanket to be had.• Morose Michell wins the wet blanket award. 