The term 'long, narrow groove' can be described as a stria, which is a five-letter word. A stria is a long, thin groove or furrow, usually found on the surface of a rock or other hard material. It is typically formed by erosion or weathering, and can also be created by the movement of glaciers. Striae are often used to study the history of a particular area, as they can provide information about the geological processes that have occurred in the past.