isotherm/ˈaɪ.səʊˌθɜː(ɹ)m/EtymologyFrom the French isotherme (“of equal temperature”, adjective), itself from Ancient Greek ἴσος (ísos, “equal”) + θέρμη (thérmē, “warmth”). By surface analysis, iso- + -therm.isotherm means A line on a graph or chart, such as a weather map, along which all the points have the same temperature. Lexicurio rates it Rare gem — a strength score of 80 out of 100.isotherm is pronounced /ˈaɪ.səʊˌθɜː(ɹ)m/.nounA line on a graph or chart, such as a weather map, along which all the points have the same temperature.