1) an apparatus for reducing speed or stopping motion e.g. of a bicycle, vehicle etc (brake)

2) (usually pl) an apparatus for reducing the effect of a collision e.g. on a railway engine (buffer)

3) a decrease in economic activity by reducing the money supply (deflation)

4) (of, holding the views of) a person who works for the welfare of human beings by reducing suffering, reforming laws about punishment etc) (humanitarian)

5) a drug made of opium, used for reducing severe pain (morphine)

6) (an instance, example, of) reducing or being reduced (reduction)

7) (an instance of) reducing a period of imprisonment; a lessening or weakening (of pain, disease, efforts etc) (remission)