An idiom which does not refer to the purchasing of plate-glass windows, or any other kind of windows for that matter. It refers instead to the act of looking at -- and usually drooling over -- items for sale, without purchasing them. In French, it is more colorfully referred to as lèche-vitrine: window-licking. Classically, people do this in a mall or similar area, where shops have windows at the front through which one can view the merchandise. However, one can also apply the term to the practice of viewing products on the World Wide Web without buying them.
As an act, window-shopping can serve any or all of several purposes:
While window-shopping is popularly viewed as a female ritual, one only has to look at male geeks drooling over the latest geek toys to find ample counterexamples.
Linguistic reference:
Burke, David. Street French 2: The Best of French Idioms. New York: John Wiley & Sons, 1996.