noun (n)

• any entry into an area not previously occupied(noun.event)

  Synonym:
  intrusion, invasion
  

  source: wordnet30
• entry to another's property without right or permission(noun.act)

  Synonym:
  intrusion, trespass, usurpation, violation
  

  source: wordnet30
• influencing strongly(noun.act)

  Synonym:
  impact, impingement
  

  source: wordnet30
• The act of entering gradually or silently upon the rights or possessions of another; unlawful intrusion.(noun)

  source: webster1913