"To peek" - means to have a sneaky look, or a quick glance at something. https://en.oxforddictionaries.com/definition/peek "To peep" - means the same thing, but can also refer to a "peeping Tom". https://en.oxforddictionaries.com/definition/peep "Peeping Tom" has a similar meaning to "voyeurism" A person who derives sexual pleasure from secretly watching people undressing or engaging in sexual activity. https://en.oxforddictionaries.com/definition/peeping_tom https://en.oxforddictionaries.com/definition/voyeurism Therefore, If you want your meaning to be understood and not be taken, as a pervert (perv). Then use the word "peek". Pervert (noun) - A person whose sexual behaviour is regarded as abnormal and unacceptable. https://en.oxforddictionaries.com/definition/pervert Hope this clarifies it for you.

The words Keek, Peek and Peep are related: keek is the most ancient form used in dialects of northern England. Peek is derived from Keek and Peep from Peek. In the majority of cases Peep and Peek are interchangeable. Maybe at times when you want to express someone is looking into someone else's personal things, then Peep may be more suitable. You would say for example "A pervert installed cameras in the women's lockers to peep at them walking in and out of the showers." Hope this helps :)