symphysis

noun4

1. •
   A place where two bones are closely joined in the median plane of the body, either forming an immovable joint (as between the pubic bones in the center of the pelvis) or completely fused (as at the midline of the lower jaw).
2. •
   A line, discernable on an X-ray, showing such fusion.
3. •
   The cartilaginous material that adjoins and facilitates the junction of such bones, without a synovial membrane.
4. •
   The process of two originally separate bones growing together as the subject matures, as with the pubic bones or lower jawbones in humans.