noun (n)

• someone who systematically obstructs some action that others want to take(noun.person)

  Synonym:
  obstructionist, obstructor, resister, thwarter
  

  source: wordnet30
• any structure that makes progress difficult(noun.artifact)

  Synonym:
  impediment, impedimenta, obstruction, obstructor
  

  source: wordnet30
• One who obstructs or hinders.(noun)

  source: webster1913