Noun, pl. diaphragms
1. In mammals, a sheet of muscle separating the thorax from the abdomen, contracted and relaxed in respiration to draw air into and expel air from the lungs; also called thoracic diaphragm.(wikipedia.org)
2. A dome-shaped, muscular partition separating the thorax from the abdomen in mammals. It plays a major role in breathing, as its contraction increases the volume of the thorax and so inflates the lungs. (Google Dictionary)
4. A contraceptive device consisting of a flexible cup, used to cover the cervix during intercourse. (wikipedia.org)
Word origin: From Ancient Greek διάφραγμα (diáphragma, “partition”); Greek dia = across, and phragma = wall.