noun (n)

• (military) an offensive against an enemy (using weapons)(noun.act)

  Synonym:
  attack, onset, onslaught
  

  source: wordnet30
• a forceful forward rush or flow(noun.event)

  Example:
  From the bow she stared at the mesmerising onrush of the sea where it split and foamed.
  The explosion interrupted the wild onrush of her thoughts.
  

  source: wordnet30
• A rushing onward.(noun)

  source: webster1913