dead on one's feet字面上来看好像是死在自己脚上，真实含义是累到哭泣；累得不能再做。

【例句】
My parents took me to Constitution Avenue to see the parade. After standing there for a whole day, my mom was so dead on her feet that she could not even cook dinner for us by the time we got home.
我爸爸妈妈带我到宪法大街去看游行。我们在那儿站了一天，回到家的时候，我妈妈的脚累得要死，连做晚饭也做不动了。

Honey, I've got to sit down and rest before I take you out to dinner. I'm really dead on my feet tonight: we had the big year-end sale on and I was so busy I didn't even have time for lunch.
亲爱的，我得坐下歇一会儿再和你一起出去吃晚饭。我今天晚上两只脚实在累死了。我们正在举行年底大减价，我忙的连午饭都没有时间吃。