Definition: The word "voyeur" (noun) refers to a person who enjoys watching others, especially when they are engaged in private activities, particularly sexual acts or when they are undressing. The word comes from French, where it means "to see."
In a more general sense, "voyeur" can also describe someone who is curious about other people's lives, not just in sexual contexts.
Voyeurism (noun): The practice or habit of being a voyeur.
Voyeuristic (adjective): Relating to or characteristic of a voyeur.
While the primary meaning of "voyeur" is related to watching sexual acts, it can also refer to someone who takes pleasure in observing others in any private or intimate situation, not necessarily sexual.
There are not many idioms or phrasal verbs directly related to "voyeur," but you can use the phrase "to keep an eye on" to describe someone who is watching something closely, though it is not limited to voyeurism.
In summary, a "voyeur" is someone who enjoys watching others in private situations, often related to sexual acts.