iris diaphragm

noun

: an adjustable diaphragm of thin opaque plates that can be turned by a ring so as to change the diameter of a central opening usually to regulate the aperture of a lens

Word History

First Known Use

1867, in the meaning defined above

Kids Definition

iris diaphragm

noun

: an adjustable diaphragm of thin plates used for changing the diameter of a central opening to control the amount of light passing (as into a microscope or camera)

Medical Definition

iris diaphragm

noun

: an adjustable diaphragm of thin opaque plates that can be turned by a ring so as to change the diameter of a central opening usually to regulate the aperture of a lens (as in a microscope)