attenˈuant noun

Anything that attenuates (also adjective)

attenˈuated adjective

1. Thin
2. Thinned
3. Dilute, rarefied
4. Tapering

attenuāˈtion noun

1. The process of making slender
2. Reduction of intensity, density, force, or (of bacteria) virulence
3. In homeopathy, the reduction of the active principles of medicines to minute doses
4. Reduction in magnitude, amplitude or intensity, arising from absorption or scattering (nuclear eng and telecommunications)

attenˈuator noun

attenuated vaccine noun (immunology)

Live bacterial or virus vaccine in which the microbes have a greatly diminished capacity to cause disease but are still able to evoke protective immunity