To croon means to sing in a soft, smooth, gentle voice, usually in a romantic or sentimental way. When someone croons a lullaby to a baby, they're singing sweetly and tenderly to help the child fall asleep. A singer might croon a love song, letting the melody flow smoothly without any harsh or loud notes.

The word became especially popular in the 1930s and 1940s when famous singers like Bing Crosby and Frank Sinatra crooned into microphones, their voices warm and intimate, as if they were singing directly to each listener. Before microphones, singers had to belt out songs loudly to fill a concert hall, but the microphone let singers croon in a more personal, conversational style.

You might hear someone croon to a pet, or even playfully croon along with a favorite song on the radio. The word suggests a certain smoothness and tenderness, like honey dripping from a spoon. When your voice croons, it glides along gently rather than belting or shouting.