This is when the lower jaw is set or pushed back to the TMJ (temporomandibular joint) which connects your mandible (lower jaw) to the skull. It can also be the result of a congenital abnormality. The outcome often sees the chin and jawline looking less pronounced (leaning inwards), less defined, and leaving you with the appearance of a weak jawline (also known as a weak jaw and / or weak chin). The edge of your chin or jaw may have a soft, rounded angle. The term might also refer to a receding chin, wherein the chin curves back toward the neck.