The Collaborative International Dictionary of English v.0.48:

Mandibular \Man*dib"u*lar\, a. [Cf. F. mandibulaire.]
   Of or pertaining to a mandible; like a mandible. -- n. The
   principal mandibular bone; the mandible.
   [1913 Webster]

   Mandibular arch (Anat.), the most anterior visceral arch,
      -- that in which the mandible is developed.
      [1913 Webster]