A big dark cloud that is carrying a storm inside it — the kind you see building up on a hot afternoon, tall and heavy and grey-black, before the rain and thunder arrive.

A big dark cloud一大片烏黑的雲 that is carrying a storm inside it裡面正醞釀著暴風雨 the kind you see building up on a hot afternoon就是你在悶熱的午後會看到逐漸堆起的那種雲 tall and heavy and grey-black又高又厚重、灰黑色 before the rain and thunder arrive在雷雨到來之前

The word is a warning word: when someone says 'look at those thunderclouds', they mean the weather is about to turn bad. Scientists have a technical name for these (cumulonimbus), but ordinary people say thundercloud. It is countable, and often plural, because a storm usually brings several.

The word is a warning word這個字帶有警告的意味 when someone says 'look at those thunderclouds'當有人說'look at those thunderclouds'（快看那些雷雨雲） they mean the weather is about to turn bad意思是天氣快要變壞了 Scientists have a technical name for these科學家對這種雲有專門的名稱 (cumulonimbus)（積雨雲cumulonimbus） but ordinary people say thundercloud但一般人會說thundercloud It is countable, and often plural這個字是可數名詞，而且常用複數 because a storm usually brings several因為一場暴風雨通常會帶來好幾朵

English also uses it for a feeling: 'a thundercloud passed over his face' means he suddenly looked very angry, and 'thunderclouds are gathering' means trouble is coming — a fight, a crisis, bad news. That second use is common in newspapers.

English also uses it for a feeling英文也用這個字來形容一種神情 'a thundercloud passed over his face' means he suddenly looked very angry'a thundercloud passed over his face'（一片烏雲掠過他臉上）意思是他突然變得很生氣 and 'thunderclouds are gathering' means trouble is coming而'thunderclouds are gathering'（烏雲正在聚集）表示麻煩要來了 a fight, a crisis, bad news像是吵架、危機，或壞消息 That second use is common in newspapers這第二種用法在報紙上很常見

You may also see it written as two words, 'thunder cloud', though one word is more usual.

You may also see it written as two words你也可能看到它被拆成兩個字寫 'thunder cloud'也就是'thunder cloud' though one word is more usual不過寫成一個字比較常見