Definition of epoch-making in English English dictionary
Constituting an epoch; opening a new era; introducing new conceptions or a new method in the treatment of a subject
highly significant or important especially bringing about or marking the beginning of a new development or era; "epochal decisions made by Roosevelt and Churchill"; "an epoch-making discovery"
An epoch-making change or declaration is considered to be the extremely important because it is likely to have a significant effect on a particular period of time. It was meant to sound like an epoch-making declaration. the epoch-making changes now taking place in Eastern Europe. very important in changing the way people live or the way a society is organized