1. significant period: a significant period in history or in somebody's life
2. start of historically significant period: the beginning of a long period of history considered particularly significant The invention of the telephone marked an epoch in the development of international communication.
3. geology unit of geologic time: a unit of geologic time that is a division of a period and is characterized by rock formation the Holocene and Pleistocene epochs of the Quaternary period
4. astronomy moment in time as reference point: a precise moment in time arbitrarily chosen as a reference point for defining the position of astronomical objects
[Early 17th century. Via modern Latin epocha< Greek epokhē "pause (in time)" < ekhein "to hold"]
