spat the dummy

Verb

spit the dummy (third-person singular simple present spits the dummy, present participle spitting the dummy, simple past and past participle spat the dummy or spit the dummy)

1. (Australia, idiomatic, informal) To overreact (as an adult) to a situation, in an angry and childish manner.
   • He'll really spit the dummy when he hears that he's not going on that trip.

   Synonyms:

   throw a tantrum, throw one's toys out of the pram