Sabotage means to deliberately damage, destroy, or interfere with something to prevent it from working properly or succeeding. When someone sabotages a project, they intentionally cause problems, often in a hidden or sneaky way.

Today, sabotage doesn't always involve physical destruction. A teammate might sabotage a group project by refusing to do their share of the work. An athlete might accidentally sabotage their own performance by staying up too late the night before a big game (called self-sabotage).

During wars, spies and resistance fighters often sabotaged enemy equipment: cutting telephone wires, damaging railroad tracks, or disabling vehicles. In World War II, resistance movements in occupied countries became famous for their sabotage operations against enemy forces.

The key element of sabotage is intention. Breaking something by accident isn't sabotage, but secretly loosening the wheels on your sister's skateboard because you're angry with her would be. Sabotage destroys trust because it's a hidden attack on something people are counting on to work.

As a noun, sabotage is the act itself (“The sabotage ruined the plan”). As a verb, to sabotage is to do it (“Someone tried to sabotage the plan”).