dreg /ˈdrɛg/
  渣滓,沈澱物,糟粕
  Dreg n.  Corrupt or defiling matter contained in a liquid, or precipitated from it; refuse; feculence; lees; grounds; sediment; hence, the vilest and most worthless part of anything; as, the dregs of society.
     We, the dregs and rubbish of mankind.   --Dryden.
  Note: ☞ Used formerly (rarely) in the singular, as by Spenser and Shakespeare, but now chiefly in the plural.
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  dreg
       n : a small amount of residue