A lozenge shaped diamond is one that is rhomboid in outline. This geometric outline is also known as "diamond" shaped, but when discussing diamonds it is best referred to with the term "lozenge" shape to avoid confusion.
Art Deco Lozenge Shape Diamond and Sapphire Ring. Photo Courtesy of Lang Antiques.
3.00 Carat Lozenge-Shaped Diamond Ring. Photo Courtesy of Lang Antiques.