Mandible. The jaw bone. The lower Jawbone in vertebrates; it is hinged to open the mouth.The 'jaw' of vertebrates responsible for crunching down food materials into a swallow-able form. Please contribute to this project, if you have more information about this term feel free to edit this page.he lower Jawbone in vertebrates; it is hinged to open the mouth.The 'jaw' of vertebrates responsible for crunching down food materials into a swallow-able form. Please contribute to this project, if you have more information about this term feel free to edit this page.