A blockade is an obstacle that stands between you and something you're trying to reach. After a robbery, police might set up a blockade around the neighborhood to catch the thief.
Anything that impedes or halts progress is a blockade. If you join the military, you might find yourself building a blockade to confine your enemies and isolate them from the outside world. If you think of the root of this word, block, then you've pretty much got the meaning right there. If you don't want your little sister to disturb the house of cards you're building in my room, you can take lots of pillows and make a fort to use as a blockade to keep her from wandering in and knocking everything over.