Definition of mainshock in English:

mainshock

noun

Seismology
  • A major earthquake that is preceded or followed by one or more smaller earthquakes; the largest of a series of shocks or earthquakes.

Origin

Mid 19th century; earliest use found in Philosophical Transactions of the Royal Society of London. From main + shock.

Pronunciation

mainshock

/ˈmeɪnʃɒk/