Definition of geochronometer in US English:

geochronometer

noun

Geology
rare
  • A feature, phenomenon, organism, etc., used as a means of dating geological events or (now historical) ascertaining the age of the earth.

Origin

Late 19th century; earliest use found in The English Mechanic. From geo- + chronometer.

Pronunciation

geochronometer

/ˌdʒiːə(ʊ)krəˈnɒmɪtə/