(n.) That which stands in the way, or opposes; anything that hinders progress; a hindrance; an obstruction, physical or moral.

bar barrier blank wall blind alley blind gut block blockade blockage bottleneck catch cecum check choking choking off clog congestion constipation cordon costiveness crimp cul-de-sac curtain dead end determent deterrent difficulty disincentive drawback embolism embolus gorge hamper hang-up hazard hindrance hitch hurdle impasse impediment infarct infarction jam joker mountain objection obstipation obstruction obstructive one small difficulty rub sealing off snag stop stoppage strangulation stumbling stumbling block stumbling stone