/euh ten'yooh ay"sheuhn/ , n.
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.
[ 1585-95; ( attenuation- (s. of attenuatio ). See ATTENUATE, -ION ]