deflate

To deflate is to let the air out of something. If you deflate the tires on your brother's bike, he won't be able to ride it until he gets them pumped up again.

deflate是指把某物里面的空气放出来。如果你给你哥哥的自行车的轮胎放气，在他给轮胎打足气之前，他就不能骑了。

to deflate a balloon/tyre

给气球/轮胎放气

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Figuratively, a person can also deflate when they are suddenly drained of self-assurance or cheer: "Hearing him criticize me in front of the class made me deflate."

比喻的说法，当一个人突然失去了自信或精神时，他也会泄气：听到他在全班面前批评我让我泄气。