1. That which was made slender, fine, or small: "The drought attenuated the river to a narrow channel."
2. Reduced in force, value, amount, or degree; weakened: "Medicine attenuated the fever's effect."
3. Rarefied or lessened by the density of.
4. In biology, bacteria or viruses) less virulent.
5. In medicine, A reference to the dilution of a solution or the reduction in virulence or toxicity of a microorganism or a drug by weakening it.
6. In electronics, to reduce the amplitude of an electrical signal with little or no distortion.