The employees were cowed into silence by the boss's harsh criticism.

cowed 是动词 cow 的过去分词形式。cow 本意是"母牛"，作为动词时表示"恐吓、威胁"，比喻像牛一样用威势压制别人。cowed 在这里表示"被吓住、被震慑"的状态。