Cartilage—A bone-like substance found in sharks, rays, ratfishes, and jawless fishes as the principle skeletal material. It is also found in other vertebrates (the tip of your nose, around the joints, ear lobes) as a support material. Cartilage is similar to bone in being calcium-based, but has greater flexibility than bone.

Cartilaginous -- A structure that is made of cartilage.

Cartilaginous skeleton - The internal, flexible support system in chondrichthyan fishes, equivalent (homologous) to the bony skeletons of other vertebrates.