Drat is a small, old-fashioned way to show you are annoyed — a very mild “oh no” when you drop something or miss the bus. It can stand alone (Drat!) or work like a verb (Drat this rain). It began as a softened swear: people used to say something much stronger, close to “God rot,” then shortened it and hid the sharp religious bit so it would not sound like real swearing. Though actually, almost nobody young says drat now. You will meet it in children’s books, in older British speech, and when someone is being playfully old-fashioned. It is polite enough for a classroom.

可惡、真是的（語氣很輕的抱怨，偏舊）