What is the meaning of defile?

noun

• A narrow pass (especially one between mountains.
  • synonyms: gorge

verb

• Place under suspicion or cast doubt upon.
  • usage: "sully someone's reputation"
  • synonyms: sully, corrupt, taint, cloud
• Make dirty or spotty, as by exposure to air; also used metaphorically.
  • usage: "The silver was tarnished by the long exposure to the air"; "Her reputation was sullied after the affair with a married man"
  • synonyms: tarnish, stain, maculate, sully
• Spot, stain, or pollute.
  • usage: "The townspeople defiled the river by emptying raw sewage into it"
  • synonyms: foul, befoul, maculate