What about slam poetry in that case, mostly built off beat poetry. Long, rambling verses that grow based on flow more than structure? Trying to define 'poetry' is hard enough, let alone trying to define it from a structure standpoint, and that really goes for any art form. Creating tidy limitations will inevitably be broken down as a new perspective comes in. What is 'poetry'? What is 'music'? What is 'art'? I don't know that creating a line between poetic pieces, such as Tom Waits Nighthawks at the Diner, for example, and strict poetry itself benefits anyone or anything in the medium itself. Obviously there's a distinction between poetry and prose, but I don't think there isn't overlap either. That O'Hara piece isn't even a disputed poem these days, but was when it came out. People even cast doubt on Ginsberg's Howl as a poem. Subjectivity is a fascinating subject.