1. Off the top of one's head 不假思索，马上
I can't tell you the figures off the top of my head. I'll have to check it up.
我无法马上告诉你具体数字，我还得查一下。
2. Off-the-wall 古怪的，离奇的
He said some really off-the-wall things. Where does he come up with them?
他说了一些非常离奇的事。他从哪里听来的？
疯狂联想：人们认为怪人都会用头撞墙bounce off the wall。
