1. Intended to be educational or tending to give instruction or advice, even when it is neither welcome nor necessary: The novel was somewhat entertaining, but it had an underlying didactic message that indicated we could learn much from history.

Some language reference books these days are considered to be less didactic than they once were.

3. Inclined to teach or to moralize excessively: The technician's didactic explanations irritated his coworkers, who simply wanted to be told how the software worked, without having to listen to long explanations about the theory and history regarding its development.
3. Containing a political or moral message: The politician's didactic speeches were usually told with the pretext of entertainment, but it was obvious that he wanted his audience to receive some moral messages from them, too.