The spelling of the phrase "haddest a tantrum" can be a bit tricky, but it is important to get it right. The word "haddest" is an old English word that means "you had" and is pronounced /ˈhædəst/. The word "tantrum" is pronounced /ˈtæntrəm/ and refers to an outburst of anger or frustration. When put together, "haddest a tantrum" means "you had an outburst of anger or frustration." It is important to spell this phrase correctly in order to communicate effectively and avoid confusion.