1. (n.) A line on a map connecting points of equal barometric pressure\, or for a certain period (mean height), as for a year; an isopiestic line.

2. (n.) The quality or state of being equal in weight, especially in atmospheric pressure. Also, the theory, method, or application of isobaric science.

air mass anticyclone artificial isotope cold front cold sector cyclone deuterium front heavy hydrogen high high-pressure area isomer isometric isometric line isopiestic line isotherm isothermal line isotone isotope low low-pressure area nuclear isomer occluded front polar front protium radioactive isotope radioisotope squall line stationary front strontium 90 warm front weather map wind-shift line