Pronunciation: (u-ten"yOO-ā'shun), [key]
1. the act of attenuating or the state of being attenuated.
2. the process by which a virus, bacterium, etc., changes under laboratory conditions to become harmless or less virulent.
3. Physics.a decrease in a property, as energy, per unit area of a wave or a beam of particles, occurring as the distance from the source increases as a result of absorption, scattering, spreading in three dimensions, etc.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.