snoop

To pry into the private affairs of others, especially by prowling about.

One who snoops.

To pry about; go about in a prying or sneaking way.

One who snoops, or pries or sneaks about; a snooper.

To be devious and cunning so as not to be seen

To secretly spy on or investigate, especially into the private personal life of others.

The act of snooping

One who snoops

A private detective

a spy who makes uninvited inquiries into the private affairs of others