noun

• (chronology, astronomy, computing) A specific instant in time, chosen as the point of reference or zero value of a system that involves identifying instants of time.
  "UNIX epoch; J2000 epoch"
• (geology) A geochronologic unit of hundreds of thousands to millions of years; a subdivision of a period, and subdivided into ages (or sometimes subepochs).
  "Now during the time of the glacial epoch the greatest distance of the sun in winter was 98¼ millions of miles, whereas it is now, in winter, only 91½ millions of miles, the mean distance being taken as 93 million miles."
• (machine learning) One complete presentation of the training data set to an iterative machine learning algorithm.
  "The neural network was trained over 500 epochs."

verb

• (sciences, transitive) To divide (data) into segments by time period.
  "The continuous data were epoched into segments of 1500 ms (starting 500 ms before visual stimulus onset), time-locked to stimulus onset (0 ms) and sorted according to experimental conditions."

noun

• (medicine) An intensive chemotherapy regimen for treating aggressive non-Hodgkin lymphoma, consisting of etoposide, prednisolone, Oncovin (vincristine), cyclophosphamide, and hydroxydaunorubicin.