Source : Webster's Revised Unabridged Dictionary (1913)

Lactonic \Lac*ton"ic\, a. [From {Lactose}.] (Chem.)
   Pertaining to, or designating, an acid obtained by the
   oxidation of milk sugar (lactose).

Lactonic \Lac*ton"ic\, a. [From {Lactone}.] (Chem.)
   Of, pertaining to, or derived from, lactone.