Then, let your students come up with their own definitions and share these with the class. I bet then we would have great definitions or perhaps great reflections of what poetry is to many. IMHO, poetry is no more words on a page than I am the Queen Elizabeth. Poetry is breathing, living, crying, laughing, feeling, loving language. It is the language that is inspired by strong thoughts, memories, and feelings.
Poetry is internalized.
I think not. Maybe I have once again undermined the art of poetry by trying to box and wrap it into a package where it just doesn't fit.