Source : Webster's Revised Unabridged Dictionary (1913)

Sublingual \Sub*lin"gual\, a. [Pref. sub + lingual: cf. F.
   sublingual.] (Anat.)
   (a) Situated under the tongue; as, the sublingual gland.
   (b) Of or pertaining to the sublingual gland; as, sublingual
       salvia.

Source : WordNet®

sublingual
     adj : beneath the tongue