To preclude something is to prevent it from happening. A muzzle precludes a dog from biting.
This is a very formal word, but it has a simple meaning: when something is precluded, it can't happen. See the prefix pre in preclude and in prevent? It is signaling that these words are all about things done before another action would happen — to make it impossible. Staying away from water precludes the possibility of drowning, though it also precludes any chance of having fun swimming.
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