One that opposes, stands in the way of, or holds up progress.(noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "obstacle" in a sentence
"a tear in my eye for the lonely man who knew well that the only obstacle to his success was the _one_ that people never _could_ see, and that the _obstacle himself_ was never _likely_ to see."
"Disorient the main obstacle is the kind of dealing with extremists"
"Sure they can, although I think the main obstacle is poverty and not over-regulation."