n. A long space of time; a secular period, either indefinite or limited to the duration of something, as a dispensation or the universe: used as equivalent to age, era, or cycle, and sometimes to eternity.n. In Platonic philosophy, a virtue, attribute, or perfection existing throughout eternity.n. The largest divisionof geologic-time: used by J. D. Dana especially in dividing the archœan into astral and archæozoic eons.