Melodramatic means exaggerated and full of overdone emotion. A reaction three sizes too big for what happened.
The word comes from melodrama, a kind of nineteenth-century play with heightened emotion and a musical accompaniment, which is where the melo comes from. Calling somebody melodramatic is a real dismissal, since it says the feeling is a performance. It is a favourite word for talking about teenagers and about opera. The noun melodrama survives both as the theatrical form and as the criticism.
1adjectivemelodramaticExaggerated in emotion or behaviour.
“There is no need to be so melodramatic about a late train.”
From melodrama + tic. Modelled after dramatic.
Etymology from Wiktionary, CC BY-SA