obstacle

(noun) something immaterial that stands in the way and must be circumvented or surmounted. Synonyms: obstruction. Examples: "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."

(noun) an obstruction that stands in the way (and must be removed or surmounted or circumvented).