The word ‘curbstone’ refers to a stone or a slab of material that forms the edge of a sidewalk or street, typically serving as a boundary between the roadway and the pedestrian walkway. It can also refer to the raised edge of a curb in a street. Additionally, in a figurative sense, ‘curbstone’ can imply something that is informal or unregulated, such as a curbstone market or a curbstone investment, which are typically conducted outside of formal regulations.
