whammy

A whammy is an unexpected surprise or twist that throws everything off balance.

Think about it like this: when you're watching a sports game and someone suddenly does something completely out of the blue - like hitting a home run in baseball or making an amazing shot in basketball - that's a whammy. It's not just a good play, it's a surprise play that makes everyone go "wow!" Whammies can happen in everyday life too: you might get an unexpected phone call from someone you haven't talked to in years, or run into an old friend on the street and suddenly have to spend hours catching up. Sometimes whammies are fun, but sometimes they're just plain annoying - like when your plans for the day get ruined because of traffic. Either way, a whammy is something that shakes things up and changes the course of events in unexpected ways.

When used as a verb, a whammy can also mean to impose a sudden or harsh penalty on someone - like if you get fined for breaking a rule at work, that's a whammied. But this usage is less common than the noun form.