[iso.bar] n [ISV is- + -bar (fr. Gk baros weight); akin to Gk barys heavy--more at grieve] (ca. 1864) 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: one of two or more atoms or elements having the same atomic weights or mass numbers but different atomic numbers