[di.a.phragm] n [ME diafragma, fr. LL diaphragma, fr. Gk, fr. diaphrassein to barricade, fr. dia- + phrassein to enclose] (14c) 1: a body partition of muscle and connective tissue; specif: the partition separating the chest and abdominal cavities in mammals
2: a dividing membrane or thin partition esp. in a tube 3 a: a more or less rigid partition in the body or shell of an invertebrate b: a transverse septum in a plant stem
4: a device that limits the aperture of a lens or optical system--compare iris diaphragm
5: a thin flexible disk (as in a microphone or loudspeaker) that vibrates when struck by sound waves or that vibrates to generate sound waves
6: a molded cap usu. of thin rubber fitted over the uterine cervix to act as a mechanical contraceptive barrier -- di.a.phrag.mat.ic adj -- di.a.phrag.mat.i.cal.ly adv