15秒记一个单词（第617个）alert

alert /?'l??t/ adj. 警惕的；警惕的；警备的:

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Tommy-音频alert.mp30:40来自Tommy教你说美语

例句/词组:

Suddenly he found himself awake and fully alert.

忽然他察觉本人醒了过去,并且高度警惕。

英语表明：

able to think quickly; quick to notice things 警惕的；警惕的；警备的: