According to Osho, 'dream' means fantasy because dreams lack causal connection with reality: ninety-nine times they miss, and the rare coincidence of a hit is mere fluke we rationalize as proof. Like Nasruddin claiming only successful arrows as his, the mind cherry-picks matches and explains away misses, turning illusions into 'truth.' Hence dream equals unreality, not dependable knowledge.
Dreams mostly miss real life, and when they accidentally match, we pretend they were true—so they’re make-believe, not reality.