shadow 指男士到下午五点的时候，脸上双颊的胡须就会重新生长出来，像一片阴影一样。five-o'clock shadow 是指男性早上刮过胡子傍晚又长出来的胡须。

【例句】
He sported a heavy five o'clock shadowfor his role.
他为了他的角色蓄起了短胡须。

Her husband has five o'clock shadow, which makes him looks much older than his real age.
她的丈夫一脸胡子，所以看起来比他的实际年龄老多了。