Source : Webster's Revised Unabridged Dictionary (1913)

Didactic \Di*dac"tic\, Didactical \Di*dac"tic*al\, a. [Gr. ?,
   fr. ? to teach; akin to L. docere to teach: cf. F.
   didactique. See {Docile}.]
   Fitted or intended to teach; conveying instruction;
   preceptive; instructive; teaching some moral lesson; as,
   didactic essays. ``Didactical writings.'' --Jer. Taylor.

         The finest didactic poem in any language. --Macaulay.

Didactic \Di*dac"tic\, n.
   A treatise on teaching or education. [Obs.] --Milton.

Source : WordNet®

didactic
     adj : instructive (especially excessively) [syn: {didactical}]