Synonyms for Pensive (same or very similar meaning)
WordNet sense 1 (persistently or morbidly thoughtful):
brooding, broody, contemplative, meditative, musing, reflective, ruminative, ponderingWordNet sense 2 (exhibiting or characterized by careful thought):
thoughtfulWordNet sense 3 (showing pensive sadness):
wistfulFrom the ODE community, based on WordNetadd/edit