Definition of diaphragm noun from the Oxford Advanced Learner's Dictionary

diaphragm

noun
ˈdaɪəfræm
 
; ˈdaɪəfræm
 
 
1 (anatomy) the layer of muscle between the lungs and the stomach, used especially to control breathing2 (British English also cap) a rubber or plastic device that a woman places inside her vagina before having sex to prevent sperm from entering the womb and making her pregnant3 any thin piece of material used to separate the parts of a machine, etc.4 (technical) a thin disc used to turn electronic signals into sound and sound into electronic signals in telephones, loudspeakers, etc.