If you are open-mouthed, your mouth has fallen wide open because you are very surprised or shocked. For a moment you are not thinking about your face; the feeling has done it for you.

If you are open-mouthed如果你是open-mouthed，your mouth has fallen wide open because you are very surprised or shocked代表你的嘴巴因為非常驚訝或震驚而張得大大的。For a moment you are not thinking about your face那一刻你根本沒在想自己的表情；the feeling has done it for you是那種感覺自己讓你的臉變成這樣的。

Writers like the picture: an open-mouthed crowd, open-mouthed amazement. People also stand open-mouthed at something huge or wonderful, so the feeling can be wonder, not only bad shock.

Writers like the picture作家喜歡這個畫面：an open-mouthed crowd, open-mouthed amazementan open-mouthed crowd（張大嘴的人群）、open-mouthed amazement（張大嘴的驚嘆）。People also stand open-mouthed at something huge or wonderful人也會因為某個巨大或美好的東西而站在那裡open-mouthed，so the feeling can be wonder, not only bad shock所以這種感覺也可以是讚嘆，不一定只是負面的震驚。

You often put it before a noun, or after stand, stare, or watch.

You often put it before a noun你常常把它放在名詞前面，or after stand, stare, or watch或是放在stand、stare、watch這些字後面。

Though actually, sleeping with your mouth open is just a mouth position — that is not what this word is usually doing. Ordinary story-like English, not a science word.

Though actually不過，sleeping with your mouth open is just a mouth position睡覺時嘴巴張開只是一種嘴巴的姿勢——that is not what this word is usually doing這個字通常不是在講這個。Ordinary story-like English, not a science word是普通、帶點故事感的英文，不是科學用字。