Term with dual meanings coined back in the early 1980's to describe "peeping toms"(1) and their objects of obsession (2). The term originated when a boy named Jon Williams became obsessed with spying on women who resided in beachside communities, and when a young sun goddess who realized she was the object of a "window-williams" began orchestrating "shows" for him which quickly led him to addiction, drove him crazy, and resulted in the boy's recurring stints in jail and rehabilitation centers. Hence, a female described as a "window-williams" is that rare female who men can become so addicted to that they lose their minds over her.
Several fictional books have been written about this true account of the original window-williams voyeur but with certain names, dates, and locations changed.
"Don't talk to him, he's a window-williams. All he wants is to find out where you live so he can get his rocks off from spying on you."
Definition 2 (most commonly used)-
"Man, he dated a hot window-williams chic and hasn't been the same since."