形容词

1. 迄今最…的；空前的；创纪录的
You use all-time when you are comparing all the things of a particular type that there have ever been. For example, if you say that something is the all-time best, you mean that it is the best thing of its type that there has ever been.

1. unsurpassed in some respect up to the present

e.g. prices at an all-time high
morale at an all-time low
among the all-time great lefthanders