Source : Webster's Revised Unabridged Dictionary (1913)

Prefrontal \Pre*fron"tal\, a. (Anat. & Zo["o]l.)
   Situated in front of the frontal bone, or the frontal region
   of the skull; ectethmoid, as a certain bone in the nasal
   capsule of many animals, and certain scales of reptiles and
   fishes. -- n. A prefrontal bone or scale.

Source : WordNet®

prefrontal
     adj : anterior to a frontal structure; "a prefrontal bone";
           "prefrontal lobes"