apex
baffle
bar
barrage
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
burden
challenge
complication
constraint
defect
disadvantage
disappointment
disaster
hardship
inconvenience
limitation
mistake
objection
peril
restraint