For it is by means of words that we apprehend, categorize, and even think and feel and know our world. When I taught my composition courses in college, I presented my classes with two theories about the relationship between language and reality. I called the one most people assume to be true the Expressive Theory, and I called the one I still think is true the Creative Theory. What this simple scheme tells us is that words come before meaning, words give rise to meaning. But once words have given rise to meaning, it seems to most of us that meaning came before words.
Poetry is art by means of words.
Though the language of poetry is the language of emotions, it is not devoid of rationality either. In a good poem the head is the head of the heart, even as it is the heart that gives life to the head. And this is true even if we accept Pascal's famous dictum about the heart having reasons that reason will not understand. Trying to define poetry is probably a useless enterprise. The literature on it is vast.