(Internet slang, dated) Windows (an operating system)

落ちる: to fall

window / (regional, dialect, Etchū region) a deep gap in a mountain ridge (so called for the way the wind blows through, like a window)

to fall / (computing) to go down (as when a computer or application becomes unresponsive) / (electrical engineering, of a circuit breaker) to trip / (informal) to fail an examination

window

a glass slide, a microscope slide

windshield, windscreen

glass ceiling

window glass; plate glass

uranium glass