noun

a hindrance or obstruction in doing something.

a serious impediment to scientific progress

hindrance,obstruction,obstacle,barrier,bar,handicap,block,check,curb,brake,restraint,restriction,limitation,encumbrance,deterrent,drawback,setback,difficulty,problem,issue,snag,catch,hitch,stumbling block,fly in the ointment,hiccup,facer,spanner in the works,monkey wrench in the works,cumber