Act up 出毛病，耍脾气，捣蛋
My car’s acting up again.
我的车又出毛病了。
His knee acted up after the marathon.
跑完法拉松后他的膝盖开始不舒服。
The kids were acting up in class.
孩子们在课堂上捣蛋。
(这个单词我竟然忘了，突然想起绝望的主妇里面就出现过这个act up)
You are going to behave today. I am not going to be humiliated in front of the entire neighborhood. And, just so you know how serious I am…Santa’s cell-phone number, I know someone who knows someone who knows an elf. And if any of you acts up, so help me, I will call Santa and I will tell him you want socks for Christmas.
你们今天得乖乖的，我不想在整条街的邻居面前丢脸。你们要知道，我不是说说而已。。。圣诞老人的手机号码，我朋友的朋友认识一个小精灵，如果今天你们谁捣蛋，相信我，我会打电话给圣诞老人，告诉他，圣诞节你们只想要袜子。
(出点小毛病是act up, 出大毛病，发生故障是break down)
Break down 发生故障，出毛病，损坏，感情失控
My car broke down.
我的车子出故障了。
Because he was being so kind and concerned, I broke down and cried...
他如此体贴关心，令我忍不住失声痛哭
