Definition of macroseism in US English:

macroseism

noun

Geology
rare
  • An earthquake, as opposed to an imperceptible earth tremor. Formerly also (in Milne's use): †a major earthquake that involved the ‘nucleus’ of the earth as well as its crust (obsolete).

Origin

Early 20th century; earliest use found in James Milne (b. 1865). From macro- + seism, partly after French macroséisme.

Pronunciation

macroseism

/ˈmakrə(ʊ)ˌsʌɪzm/