1) Nordstrom dick 
A store detective (sometimes called a SD) is a member of Loss Prevention whose main role is to prevent and detect theft (commonly known as shoplifting) and reduce shrink in retail outlets. They do this by patroling the store in plains clothes looking to identify members of the public who are stealing from the store. More common terms today with ma...
[n] - a private detective employed by a merchant to stop pilferage
noun a private detective employed by a merchant to stop pilferage