pilferer
/ˈpɪlfərər/Definitions
1. noun
A person who steals or pilfers, especially in a stealthy or habitual manner.
“The store owner suspected that a pilferer was hiding in the shadows, watching for an opportunity to steal.”
2. verb
To steal or pilfer, especially in a stealthy or habitual manner.
“She pilfered a few candies from the jar without anyone noticing.”