Imbrication: The weather-tight covering formed by overlapping rows of plain or end-modified tiles or shingles thereby producing distinctive surface patterns.
From the Old-House Dictionary, by Steven J. Phillips
Imbrication is often seen in Victorian-style houses, and the “modified” shingles are identified by the end shape of the shingle. For example, look at the shingles in the gable end roof of the photo above. Starting from the top then going down, there are five different rows of shingles types: square, diamond, octagonal, fish scale and square again. Overall, Phillips has identified nine types of imbrication styles.