To prevent or hinder the progress of something. The sudden change in regulations stymied the company's expansion plans.
To perplex or stump, making it difficult to find a solution. The tricky puzzle has stymied experts for years.
(Golf, historical) To block an opponent's line to the hole by positioning one's ball directly between their ball and the hole. Trying to protect his slim lead, he stymied his rival on the final green.