Snoop (verb)

To investigate or look around furtively, especially in order to find out something private.

Origin:

Late 17th century: probably from low german snoepen "eat on the sly"; related to low german snoep "sweetmeat".

Examples:

1. She snooped around in his room when he was out.
2. He snooped through her diary when she wasn't looking.
3. She snooped in his phone when he was in the shower.
4. The detective snooped around the crime scene.
5. The reporter snooped around the company to uncover the scandal.