Synonyms for Obstruction (same or very similar meaning)
WordNet sense 1 (the state or condition of being obstructed):
blockageWordNet sense 2 (something immaterial that stands in the way and must be circumvented or surmounted):
obstacleWordNet sense 3 (any structure that makes progress difficult):
impediment, impedimenta, obstructer, obstructorFrom the ODE community, based on WordNetadd/edit