It's not possible to provide a hard and fast definition of Romantic poetry, but we can still identify some notable characteristics all the same. The Romantic approach to poetry was marked by a tendency to abandon the quite formal, rigid standards of Neo-Classicism, both in relation to prosody and subject matter. The Romantics consciously broke with this tradition, creating an entirely new poetic language of their own.
Up until the late 18th century or so, it was widely thought that poetry should strive for objectivity, emulating an unchanging natural order that provided much-needed stability and moral guidance in human lives. Unlike their Neo-Classical forbears, however, the Romantics did not attempt to mirror the world around them, but they attempted to express their individual selves. They embraced a more subjective style of poetry, one that was concerned with the unique and the strange, the unusual and the idiosyncratic. The emotional life of the poet—his loves, his feelings, his desires—became an acceptable subject matter in its own right. What had once been thought self-indulgent and eccentric was suddenly elevated to a high art form.
A notable feature of Romantic poetry, especially in the early work of Wordsworth, was the way in which it often dealt with the lives of ordinary working people. The tenets of Neo-Classicism had held that such uncultivated lives—nasty, brutish, and short—were hardly a fit subject for poetry. Yet in works such as Wordsworth's "Lucy" poems and "Resolution and Independence," we are treated to a sympathetic portrayal of the rural poor, whose harsh, stunted lives provide ample material for an elevated insight into the human condition.
The role of nature took on huge significance for the Romantics. The natural world was regarded as almost a force in its own right, complete with its own unique personality. Nature wasn't just an object of study, or something pretty to look at; it had the power to inspire, to meld with the individual poet's imagination to conjure up a deeply philosophical vision. As Wordsworth wrote in "Tintern Abbey":
And I have felt A presence that disturbs me with the joy Of elevated thoughts; a sense sublime Of something far more deeply interfused, Whose dwelling is the light of setting suns, And the round ocean and the living air, And the blue sky, and in the mind of man: A motion and a spirit, that impels All thinking things, all objects of all thought, And rolls through all things.
Neo-Classicism distrusted the imagination, seeing it as leading to flights of self-indulgent fancy. Yet for the Romantics, it was a faculty whose free exercise was essential for the creation of art. The imagination combined with nature to generate poetry of depth and sublimity, which gave the fullest expression to all elements of the human soul, both rational and instinctual. Romantic poetry was holistic, rejecting the more narrowly rationalistic approach of Neo-Classicism to embrace the whole person.