Definition: A microtonal lowering of the 3rd, 7th, or 5th scale degrees, characteristic of jazz and blues. On the piano, this is often approximated by playing the minor interval against the major harmony.
The Savvy Take: Since we can’t bend pitch on a piano, we have to cheat. We often “crush” the minor key and slide off it onto the major key quickly. It’s that friction—the clash between the minor melody and major chord—that creates the “blue” feeling.