What is the meaning of backwash?

noun

• The flow of air that is driven backwards by an aircraft propeller.
  • synonyms: slipstream, airstream, race, wash
• The consequences of an event (especially a catastrophic event. )
  • usage: "the aftermath of war"; "in the wake of the accident no one knew how many had been injured"
  • synonyms: aftermath, wake
• The wave that spreads behind a boat as it moves forward.
  • usage: "the motorboat's wake capsized the canoe"
  • synonyms: wake