a drink, usually an alcoholic one, that you have quickly

We stopped in Covent Garden for a swifty and a snack. 我们在科文特花园停下来很快地喝了一杯，还吃了点东西。

something that you do suddenly, without giving any warning that you are going to do it

If you're playing with people you don't know too well, they can pull a swifty, change the key of a song, and suddenly you're singing badly and you can't work out why. 如果你和不太熟悉的人在一起玩，他们可能突然做点什么，把歌的调子变了，突然间你唱得很糟糕，却又不知道为什么。