You said it! : I agree completely，what you said is especially true；You are absolutely right, I couldn’t agree more. If you response this to someone,which means you agree with what has just been said .This colloquial（通俗的） Americanism dates from the first half of the 1900s. As in You should have a career plan before graduating—You said it!
中文释义：“You said it!”通常意为“你还真说着了”,也就是“真是这样，千真万确,说到点子上了”的意思，表示肯定前一个说话人的意见。另外，“You said it!” 是极为地道的英语口语表达，我们经常会在看电影或者是在英语节目的时候碰见，其实它的意思跟“I can’t agree with you more.” 有着相似之处。例句：Don’t forget to do exercise every day if you want to keep fit.–You said it! （别忘记每天运动，如果你想保持身体健康。–你说得对！）与此类似的表达还有as you said，含义为“正如你所说”，通常表示引用或者再次提及。