Drury, J. The poetry dictionary, c2006 (Didactic poetry: Poetry that teaches something; more specifically, poetry whose primary purpose is to instruct)
Cuddon, J. A dictionary of literary terms, 1982 (Didactic: Any work of literature which sets out to instruct may be called didactic. Didactic poetry is almost a special category of its own)
Harmon, J. A handbook to literature, c2006 (Didactic poetry: Poetry that is intended primarily to teach a lesson)

Poems that are intended to be instructional.