All-important means extremely important — so important that other things wait for it. People use it for the one thing that seems to decide the result: the all-important last question, the all-important first impression, the all-important vote. It is stronger and a little more dramatic than very important. You hear it in news, in sport, in school talk, and in writing. It can sound like a headline: everything cannot really be all-important, though actually speakers stretch it when they want you to feel the weight of one moment. The all- here means completely, in every way, not all the people.