let down

基本解释

The plane let down gently before landing at the airport.
飞机在机场着陆以前徐徐下降。
She wanted to have her skirt let down several centimetres.
她想把裙子放长几厘米。
http://dict.hjenglish.com
If Rapunzel simply let down her hair and the prince started climbing immediately, her hair would not break, but it might rip out.
如果长发公主刚将她的头发放下王子就立刻攀爬的话，她的头发就不会断，但是，它很有可能会被拔掉。

"We have now to concretize the measure which have been agreed upon 11 April and we have to send a clear signal that we will not let down Greece, and I think that is the bottom line of everything."
So I'm going to comment those out, and let's go down to this piece of code, and uncomment it.
那么我会把这些注释上，让我们看看这段代码，取消注释。
麻省理工公开课 - 计算机科学及编程导论课程节选
So let me write that down, it's how much memory do I need to complete a computation.
让我把它写下来,当我计算的时候。
麻省理工公开课 - 计算机科学及编程导论课程节选

Some newspaper and magazine companies, feeling let down by the Kindle electronic reader from Amazon.com Inc.
FORBES: Where the Kindle's real muscle lies

If you let someone down, you disappoint them, by not doing something that you have said you will do or that they expected you to do.
let down
If something lets you down, it is the reason you are not as successful as you could have been.