isochron

noun

iso·​chron ˈī-sə-ˌkrän 

variants or isochrone

ˈī-sə-ˌkrōn 

: an imaginary line or a line on a chart connecting points at which an event occurs simultaneously or which represents the same time or time difference

Word History

Etymology

International Scientific Vocabulary is- + -chron (from Greek chronos time)

First Known Use

1881, in the meaning defined above