from http://www.poetryfoundation.org/harriet/2013/09/flavorwire-for-your-monday-20-poets-on-the-meaning-of-poetry/ - plus many more poets ...
From Carl Sandburg’s “Tentative (First Model): Definitions of Poetry”:
1. Poetry is a projection across silence of cadences arranged to break that silence with definite intentions of echoes, syllables, wave lengths.
2. Poetry is an art practised with the terribly plastic material of human language.
3. Poetry is the report of a nuance between two moments, when people say, ‘Listen!’ and ‘Did you see it’ ‘Did you hear it? What was it?’
4. Poetry is the tracing of the trajectories of a finite sound to the infinite points of its echoes.
5. Poetry is a sequence of dots and dashes, spelling depths, crypts, cross-lights, and moon wisps.
6. Poetry is a puppet-show, where riders of skyrockets and divers of sea fathoms gossip about the sixth sense and the fourth dimension.
7. Poetry is a plan for a slit in the face of a bronze fountain goat and the path of fresh drinking water.
8. Poetry is a slipknot tightened around a time-beat of one thought, two thoughts, and a last interweaving thought there is not yet a number for.
9. Poetry is an echo asking a shadow dancer to be a partner.
10. Poetry is the journal of a sea animal living on land, wanting to fly