To reduce in quality or purity.
To reduce in altitude or magnitude, as hills and mountains; to wear down.
To lower in value or social position.
To purify; reduce to a fine, unmixed, or pure state; to free from impurities.
To improve in accuracy, delicacy, or excellence.
To become pure; to be cleared of impure matter.
To purify of coarseness, vulgarity, inelegance, etc.; to polish.
To make nice or subtle.