fast asleep [ˌfɑ:st 'əsli:p]

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附加级

熟睡

The boy was fast asleep before the bedtime story was finished.这个男孩没等临睡前的故事讲完就睡熟了。
He was lying prone on the couch,fast asleep.他趴在长沙发椅上，睡得很熟。