a person who obtains sexual gratification by looking at other people's sexual organs, sexual acts, etc
a prying observer who gets excitement from witnessing other people's suffering or distress
There are some disasters that are so ghastly that even the voyeur averts the eyes — Guardian
voyeurism /ʹvwahyəriz(ə)m/ noun
voyeuristic /-ʹristik/ adj
voyeuristically /-ʹristikli/ adv
[French voyeur, literally ‘one who sees’, from voir to see, from Latin vidēre]