The Collaborative International Dictionary of English v.0.48:

Romanticism \Ro*man"ti*cism\, n. [CF. It. romanticismo, F.
   romantisme, romanticisme.]
   A fondness for romantic characteristics or peculiarities;
   specifically, in modern literature, an aiming at romantic
   effects; -- applied to the productions of a school of writers
   who sought to revive certain medi?val forms and methods in
   opposition to the so-called classical style.
   [1913 Webster]

         He [Lessing] may be said to have begun the revolt from
         pseudo-classicism in poetry, and to have been thus
         unconsciously the founder of romanticism. --Lowell.
   [1913 Webster]

WordNet (r) 3.0 (2006):

romanticism
    n 1: impractical romantic ideals and attitudes
    2: a movement in literature and art during the late 18th and
       early 19th centuries that celebrated nature rather than
       civilization; "Romanticism valued imagination and emotion
       over rationality" [syn: Romanticism, Romantic Movement]
       [ant: classicalism, classicism]
    3: an exciting and mysterious quality (as of a heroic time or
       adventure) [syn: romanticism, romance]