WordWeb Online

1. Not fanciful or imaginative
   "a prosaic and unimaginative essay";
   - matter-of-fact
    
2. Lacking wit or imagination
   "a prosaic movie plot";
   - pedestrian, prosy, earthbound
    
3. Not challenging; dull and lacking excitement
   - commonplace, humdrum, unglamorous, unglamourous [Brit, non-standard], mundane

See also: lame, lameo [informal], meh [informal], unexciting, uninspiring, uninteresting, unrhetorical

Encyclopedia: Prosaic