What is the meaning of onslaught?

noun

• A sudden and severe onset of trouble.
• Military) an offensive against an enemy (using weapons. ()
  • usage: "the attack began at dawn"
  • synonyms: attack, onset, onrush
• The rapid and continuous delivery of linguistic communication (spoken or written. )
  • usage: "a barrage of questions"; "a bombardment of mail complaining about his mistake"
  • synonyms: barrage, bombardment, outpouring