Mirth/mɜːrθ/ Definition 1 of 1Pro Tip 1/3Positive Emotion Mirth implies a deep, joyful emotion often shown with laughter. His joke was met with great mirth. Pro Tip 2/3Social Settings Use 'mirth' to describe lively joy in groups, like parties or family gatherings. There was an air of mirth at the reunion. Pro Tip 3/3Not Sarcastic Mirth is genuine happiness, not sarcastic or mocking laughter. Her mirth was contagious, and soon everyone was laughing.