stop something from happening
thwart - stop
To 'thwart' means to successfully block or delay something, or prevent somebody from getting what they want. This formal word is often used in a positive sense, usually in relation to somebody doing something heroic to prevent something bad from happening, or the evil machinations of another. However, if you are the one being thwarted, it can be a source of great frustration.
Thanks to their diligent work and first-rate intelligence gathering, the police managed to thwart the terrorists before they could carry out their planned attack.
I was thwarted in my efforts to revamp the department by the obstinacy and recalcitrance of upper management.
My goal of running the marathon was thwarted soon after the race began when I picked up a nasty injury which meant I had to drop out.