Grasping at the Indefinable
There are as many definitions of poetry as there are poets. Wordsworth defined poetry as "the spontaneous overflow of powerful feelings;" Emily Dickinson said, "If I read a book and it makes my body so cold no fire ever can warm me, I know that is poetry;" and Dylan Thomas defined poetry this way: "Poetry is what makes me laugh or cry or yawn, what makes my toenails twinkle, what makes me want to do this or that or nothing."Poetry is the chiseled marble of language; it's a paint-spattered canvas - but the poet uses words instead of paint, and the canvas is you.
Poetry is evocative. It typically evokes in the reader an intense emotion: joy, sorrow, anger, catharsis, love
One of the most definable characteristics of the poetic form is economy of language, considering a word's emotive qualities, its musical value, its spacing, and yes, even its spacial relationship to the page.
There's your definition of poetry. Because defining poetry is like grasping at the wind - once you catch it, it's no longer wind.