不ふ沈ちん艦かんMeanings1noununsinkable battleshipRefers to a warship designed or believed to be unsinkable; often used historically or metaphorically.戦艦大和せんかんやまとは不ふ沈ちん艦かんと信しんじられていた。The battleship Yamato was believed to be an unsinkable battleship.