Free verse, or vers libre, is a common type of unrhymed poetry. The form is defined as rhythmical lines varying in length, adhering to no fixed metrical pattern and usually unrhymed. The pattern is often largely based on repetition and parallel grammatical structure. Although at first glance free verse may appear unrestrained, as T.S. Eliot (a practitioner) said, "No vers is libre for the man who wants to do a good job."
Whitman’s "A Noiseless Patient Spider" is one example, and Arnold’s "Dover Beach" is another (although less typical because it uses rhyme). Thoroughly typical is Whitman’s "When I Heard the Learn’d Astronomer".