1) Looker 2) Paraphilia 3) Spectator 4) Viewer 5) Voyeuristical 6) Watcher 7) Witness 1) Voyeuristical 
[adj] - of or relating to voyeurs or voyeurism
voyeuristic A reference to watching a person undress, or who is nude, without the 'victim' being aware of such observations. It is considered by psychiatrists to be one of the paraphilias (sexual deviations or sexual perversions) within the group of psychosexual disorders.
voyeuristical adjective of or relating to voyeurs or voyeurism; `his voyeuristic pleasures`