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.
out of the window
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]