Pursuing illusionary goals, trying to achieve impossible things. The term comes from the old tale about finding a crock of gold if one digs at the end of the rainbow, where it touches earth. The idea of chasing rainbows as equivalent to a fruitless quest was expressed in the nineteenth century; those who did so were called “rainbow chasers.” A popular song, “I’m Always Chasing Rainbows,” with words by Joseph McCarthy and music by Harry Carroll (based on Chopin’s C-sharp minor Fantasy Impromptu), was published in 1918. It was used in several motion pictures, among them Ziegfeld Girl, with Judy Garland, and was revived with considerable success in 1946.