noun
Meteorological term for the boundary between polar and tropical air masses.
極前線は、寒帯気団と熱帯気団の境界に形成される。
The polar front forms at the boundary between polar and tropical air masses.
Compound of 極 (きょく, 'pole') and 前線 (ぜんせん, 'front'), a calque of English 'polar front'.