sharpen one's spear only before going into battle;grind the spear just before a battle;make last-minute preparation that would [might] prove too late;sharpen one's spear in the face of an on-coming encounter;start to prepare only at the last moment; without due preparation
I have to cram all night for tomorrow ' s exams 为了明天的考试，我得熬夜临阵磨枪。
2.
I have a deadline for friday and i ' m going to have to cram to get it all done 截止日是周五，所以，我临阵磨枪兴许还来得及。
3.
But now we can no longer risk emergency improvisation of national defense ; we have been compelled to create a permanent armaments industry of vast proportions 但是现在我们不能再以临阵磨枪的方式承担国防上的风险；我们已被迫创建一个规模宏大的永久性军事工业。
4.
Allocate to the time of each homework , review way , to reviewed plan , the processing to all sorts of relevant things must accomplish know fairly well , lest start to prepare at the last moment , from random condition 对各门功课的时间分配、复习方式，对复习的进度，对各种相关事情的处理一定要做到心中有数，以免临阵磨枪，自乱阵脚。
