The noun obstacle has 2 senses (first 2 from tagged texts)
1. (5) obstacle, obstruction -- (something immaterial that stands in the way and must be circumvented or surmounted; "lack of imagination is an obstacle to one's advancement"; "the poverty of a district is an obstacle to good education"; "the filibuster was a major obstruction to the success of their plan")
2. (4) obstacle -- (an obstruction that stands in the way (and must be removed or surmounted or circumvented))