ˈ ̷ ̷ ̷ ̷ at iso- +ˌbär noun
Etymology: International Scientific Vocabulary is- + -bar (from Greek baros weight) — more at grieve
1. : an imaginary line or a line on a map or chart connecting or marking places on the surface of the earth where the height of the barometer reduced to sea level is the same either at a given time or for a certain period
2.
a. also iso·bare -ˌba(a)(ə)r : one of two or more atoms having practically the same atomic weights but different atomic numbers and hence different chemical properties
carbon 14 and ordinary nitrogen 14 are isobars
b. : one of two or more nuclides having the same mass numbers but different atomic numbers
• iso·bar·ism -ˌbäˌrizəm, -ˌba(a)ˌr- noun -s