a barrier of objects (e.g. sacks of sand) put in front of something as a defence

blocking object

something (e.g. a gate, bar, objects) that prevents or controls progress or movement

obstruction

the surrounding of a place e.g. by armies or warships, to stop goods or people from entering or leaving

barrier

an operation of armed forces who surround a town etc and prevent supplies from going in

barrier

(to cause a person, machine etc) to put an end to action, movement, progress etc; to prevent a person, thing

end, halt; impediment