Feeling smiley. It's since become known as the 'felt' or 'Duchenne' smile and it's associated with genuine feelings of pleasure and giddy happiness. The smile is long and intense, though it involves the contraction of just two muscles. an expression on the face in which the ends of the mouth curve up slightly, often with the lips moving apart so that the teeth can be seen, expressing esp. happiness, pleasure, amusement, or a friendly feeling: