The area/by the window; a seat next to a window. Figuratively, it can mean being sidelined at work.
コンサートでは窓際の席を予約しておいた。
I reserved a seat by the window for the concert.
窓際に座って外の景色を眺めるのが好きだ。
I like sitting by the window and looking at the outside view.
彼は部署異動で窓際に追いやられたと言われている。
It is said that he was pushed to a sidelined position after the department transfer.