A person who derives sexual pleasure from secretly watching people undressing or engaging in sexual activity.
That Peeping Tom is always watching people undress.
Is a male who downloads pictures of a females from their social media without their knowledge and using the photo to masturbate.
Girl: uploads new profile picture from church event
Guy: downloads picture of girl he doesn’t speak to onto his phone and self pleasures themselves without other person ever knowing
Richard was a peeping Tom while his girlfriend slept.