Oneiric is an adjective that describes things related to dreams. At the end of "The Wizard of Oz," you are left to decide if Dorothy really traveled to Oz or if she was simply in an oneiric state, dreaming up the whole adventure.
Oneiric comes from the Greek word oneiros, meaning a dream. In Greek mythology, the Oneiroi, or Dreams, were the brothers (or sons, depending on the author) of Hypnos, or Sleep. Homer, Ovid, and Euripides all wrote about them — Homer in both the "Odyssey" and the "Iliad." The adjective oneiric is often used in film theory to describe the dream-like elements of a movie.