This is the 15808th most frequent Polish word.
słoik
"Jar" (a container typically made of glass used for storing food or other items).
Here, 'słoik' is used to denote a physical object, a jar used for storing items, most commonly food.
Zostały trzy słoiki dżemu na półce.
There are three jars of jam left on the shelf.
In this context, 'słoik' is used colloquially to refer to people who bring jars of food from their home regions to the capital city.
Warszawiacy często nazywają przyjezdnych 'słoikami'.
People in Warsaw often call newcomers 'jars'.
Here, 'słoik' refers once again to a physical container, specifically jars intended for preserving compote.