8 letters · 13 points in Scrabble
noun (meteorology) an isogram connecting points having the same temperature at a given time
originFrom the French isotherme (“of equal temperature”, adjective), itself from Ancient Greek ἴσος (ísos, “equal”) + θέρμη (thérmē, “warmth”). By surface analysis, iso- + -therm.
Etymology from Wiktionary, CC BY-SA 3.0