Diaphragm/ˈdaɪəfræm/ Definition 1 of 3Pro Tip 1/3Breathing Muscle The diaphragm is essential for breathing; it moves rhythmically with each breath. She took a deep breath, and her diaphragm expanded. Pro Tip 2/3Emotion Indicator The movement of the diaphragm can indicate laughter or heavy breathing due to emotions. His diaphragm jerked with suppressed giggles. Pro Tip 3/3Voice Support Singers often speak of the diaphragm as a support for a strong and controlled voice. To hit the high notes, she engaged her diaphragm more firmly.