Here are some accepted definitions of Romanticism, from academic sources.
From the University of Toronto Glossary of Literary terms:
http://www.library.utoronto.ca/utel/glossary/Romanticism.html
A movement of the late eighteenth century and the nineteenth century that exalts individualism over collectivism, revolutionism over conservatism, innovation over tradition, imagination over reason, and spontaneity over constraint. According to romanticism, art is essentially self-expression, a spontaneous overflow of powerful emotions. A work of art should exemplify organic form so that the parts and the whole are vitally interdependent. Romanticism strives to heal the cleavage between subject and object, "to make the external internal, the internal external, to make nature thought, and thought nature" (Samuel Taylor Coleridge). As a political idea, Romanticism stresses the innate goodness of human beings and the evil of the institutions that trammel and stultify human creativity.
From Gale Free Resources Glossary of Literary Terms:
http://www.galegroup.com/free_resources/glossary/glossary_qr.htm#r
This term has two widely accepted meanings. In historical criticism, it refers to a European intellectual and artistic movement of the late eighteenth and early nineteenth centuries that sought greater freedom of personal expression than that allowed by the strict rules of literary form and logic of the eighteenth-century neoclassicists. The Romantics preferred emotional and imaginative expression to rational analysis. They considered the individual to be at the center of all experience and so placed him or her at the center of their art. The Romantics believed that the creative imagination reveals nobler truths — unique feelings and attitudes — than those that could be discovered by logic or by scientific examination. Both the natural world and the state of childhood were important sources for revelations of "eternal truths." "Romanticism" is also used as a general term to refer to a type of sensibility found in all periods of literary history and usually considered to be in opposition to the principles of classicism. In this sense, Romanticism signifies any work or philosophy in which the exotic or dreamlike figure strongly, or that is devoted to individualistic expression, self-analysis, or a pursuit of a higher realm of knowledge than can be discovered by human reason. Prominent Romantics include Jean-Jacques Rousseau, William Wordsworth, John Keats, Lord Byron, and Johann Wolfgang von Goethe. (Compare with Neoclassicism, and Transcendentalism.)
Extract from the Bedford Glossary of Literary Terms, 2nd Ed. (2003):
Broadly speaking, a term applicable to philosophy, politics, and the arts in general. Even when specifically applied to literature, romanticism cannot be strictly defined, for it has been used in a wide variety of ways. The diverse and even dissimilar nature of works commonly said to be romantic, however, is actually in keeping with romanticism's emphasis on subjective experience, innovation, imagination, and the individual. The term romantic was first used to characterize narratives called romances that arose in medieval times; these stories often featured improbable plots, hence the (often pejorative) connotation of romantic as "implausible." In the eighteenth century, the term was frequently used to describe melancholy works with exotic settings and situations. . . . German philosopher and critic Friedrich Schlegel was the first to apply the term to a literary movement that opposed neoclassicism (called die Klassik in German), which emphasized qualities such as reason, order, restraint, balance, and clarity in emulation of classical literature. . . . The so-called Romantic Period or movement is generally considered to extend from the end of the eighteenth century through much of the nineteenth century, depending on which country's romantic movement is being discussed. Most critics agree that romanticism arose first in Germany and England, followed by America and other European countries such as France. . . .