Main Entry: iso·bar

Pronunciation: \ˈī-sə-ˌbär\

Function: noun

Etymology: International Scientific Vocabulary is- + -bar (from Greek baros weight); akin to Greek barys heavy — more at grieve

Date: circa 1864

1 : an imaginary line or a line on a map or chart connecting or marking places of equal barometric pressure
2 : one of two or more atoms or elements having the same atomic weights or mass numbers but different atomic numbers

[isobar illustration]