A barricade is anything that prevents people or vehicles from getting through. Construction workers often barricade a street to block traffic.
You know how barriers block things from getting through? A barricade is similar. Soldiers create barricades to keep enemy troops out. Police officers put up barricades around a crime scene. If an electrical wire becomes loose and dangerous, a barricade around the area will keep people from getting hurt. This can also be a verb, like when parents barricade part of their house to keep toddlers from getting into trouble. Barricading is a physical way of saying "Keep out!"