noun (n)

• any structure that makes progress difficult(noun.artifact)

  Synonym:
  impediment, impedimenta, obstructer, obstructor
  

  source: wordnet30
• the physical condition of blocking or filling a passage with an obstruction(noun.state)

  Synonym:
  blockage
  

  source: wordnet30
• something immaterial that stands in the way and must be circumvented or surmounted(noun.cognition)

  Example:
  The filibuster was a major obstruction to the success of their plan.
  

  Synonym:
  obstacle
  

  source: wordnet30
• the act of obstructing(noun.act)

  Example:
  Obstruction of justice.
  

  source: wordnet30
• getting in someone's way(noun.act)

  source: wordnet30
• The act of obstructing, or state of being obstructed.(noun)

  source: webster1913