n. 1. A particular period of history, especially one considered remarkable or noteworthy. 2. A unit of geologic time that is a division of a period. 3. Astronomy An instant in time that is arbitrarily selected as a point of reference for specification of celestial coordinates. [Medieval Latin epocha, measure of time, from Greek epokhē, a point in time; see segh- in the Appendix of Indo-European roots.] |
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