(of a part of the body) to be reduced in size and therefore strength, or, more generally, to become weaker

After several months in a hospital bed, my leg muscles had atrophied. 我在医院病床上呆了几个月后，腿部肌肉已经萎缩了。

In the 1980s, their political power gradually atrophied (= became weaker). 20世纪80年代他们的政治权力逐渐衰落。