Free verse is poetry not dictated by an established form or meter and often influenced by the rhythms of speech.
From A Poet’s Glossary
The following definition of the term free verse is reprinted from A Poet's Glossary by Edward Hirsch.
A poetry of organic rhythms, of deliberate irregularity, improvisatory delight. Free verse is a form of nonmetrical writing that takes pleasure in a various and emergent verbal music. “As regarding rhythm,” Ezra Pound writes in “A Retrospect” (1918): “to compose in the sequence of the musical phrase, not in sequence of a metronome.” Free verse is often inspired by the cadence—the natural rhythm, the inner tune—of spoken language. It possesses visual form and uses the graphic line to differentiate itself from prose. “The words are more poised than in prose,” Louis MacNeice states in Modern Poetry (1938); “they are not only, like the words in typical prose, contributory to the total effect, but are to be attended to, in passing, for their own sake.” The dream of free verse: an originary verbal music for every poem. Jorge Luis Borges explains: “Beyond its rhythm, the typographical appearance of free verse informs the reader that what lies in store for him is not information or reasoning but emotion.”
The term free verse is a literal translation of vers libre, which was employed by French symbolist poets seeking freedom from the strictures of the alexandrine. It has antecedents in medieval alliterative verse, in highly rhythmic and rhymed prose, in Milton’s liberated blank-verse lines and verse paragraphs. But the greatest antecedent is the King James versions of the Psalms and the Song of Songs, based in part on the original Hebrew cadences. The rhetorical parallelism and expansive repetitions of the Hebrew Bible inspired Christopher Smart, who created his own canticles of praise in Jubilate Agno (1759–1763); William Blake, whose long-lined visionary poems have the power of prophetic utterance; and Walt Whitman, the progenitor of American free verse, who hungered for a line large enough to express the totality of life:
My voice goes after what my eyes cannot reach,
With the twirl of my tongue I encompass worlds and volumes of worlds.
Speech is the twin of my vision, it is unequal to measure itself...
Whitman’s rhythms directly influenced Gerard Manley Hopkins’s long-lined metrical experiments and William Carlos Williams’s exercises in a new measure, the three-ply line and the variable foot. They are an influence, mostly repressed, on T. S. Eliot, who initiated modern poetry with the iambic-based free-verse rhythms of “The Love Song of J. Alfred Prufrock” (1920), and Ezra Pound, whose poem “The Return” (1912) W. B. Yeats praised as the “most beautiful poem that has been written in the free form, one of the few in which I find real organic rhythms.” Some of Whitman’s international progeny: Apollinaire (France), Pessoa (Portugal), Lorca (Spain), Vallejo (Peru), Neruda (Chile), Paz (Mexico), Borges (Argentina), Martí (Cuba), Darío (Nicaragua). Whitman leads a long line of visionary poets, such as Hart Crane and D. H. Lawrence, Galway Kinnell, Gerald Stern, and Muriel Rukeyser. Formally, Whitman is the progenitor of C. K. Williams’s rangy inclusive cadences and Charles Wright’s use of a two-part dropped line, a long line with an additional rhythmic (and spatial) thrust. So, too, Whitman stands behind the improvisatory free-verse rhythms of such poets as Langston Hughes, Philip Levine, and Michael Harper, all influenced by jazz, and such New York poets as Frank O’Hara, John Ashbery, and James Schuyler, all influenced by abstract expressionism. Jazz and action painting are two good American analogues for modern free verse.
“If one thinks of the literal root of the word verse, ‘a line, furrow, turning—vertere, to turn . . . ,’ he will come to a sense of ‘free verse’ as that instance of writing in poetry which ‘turns’ upon an occasion intimate with, in fact, the issue of its own nature,” Robert Creeley explains in “Notes Apropos ‘Free Verse’ ” (1966). Free verse also turns in the space of short-lined poems. The short line often gives a feeling that something has been taken away, which has proved especially suitable for poems of loss. It can also give the feeling of clearing away the clutter and has thus proved useful for the imagist poems of T. E. Hulme, F. S. Flint, and H. D., and the objectivist works of George Oppen, Charles Reznikoff, and Louis Zukofsky. As the length of the lines varies in free-verse poems, so the reader participates in the making of poetic thought. The free-verse poem fits no mold; it has no preexistent pattern. The reader supplies the verbal speeds, intonations, emphasis. Or as Frank O’Hara says: “You just go on your nerve.”