out (of) the window

Forgotten or disregarded; lost or wasted. One member of the audience started shouting at the speaker during the presentation, and all sense of decorum went right out of the window. Once the government deregulated the industry, expensive safety precautions were the first thing out the window.

Fig. gone; wasted. All that work gone out the window because my computer crashed. My forty dollars—out the window! Why didn't I save my money?

Discarded, tossed out. This term is often used in the phrase go out the window, as in For the town planners past experience seems to have gone out the window. It alludes to unwanted items being hurled out of the window. [First half of 1900s]

Discarded, gone forever. The transfer from objects thrown or dropped out of a window to ideas and other more ephemeral things took place in the seventeenth century. Dickens played with it in Pickwick Papers: “‘I am ruminating,’ said Mr. Pickwick, ‘on the strange mutability of human affairs.’—‘Ah, I see—in at the palace door one day, out at the window the next. Philosopher, sir?’—‘An observer of human nature, sir,’ said Mr. Pickwick.”