To bedevil means to cause someone persistent trouble or confusion, like a problem that keeps bothering you no matter what you try. The word describes being plagued by difficulties that won't go away, troubles that persist despite your efforts to resolve them.

A student might be bedeviled by long division, struggling with it week after week despite extra practice. A basketball team could be bedeviled by turnovers, making the same mistakes game after game. Scientists are often bedeviled by questions they can't yet answer, problems that resist every approach they try.

When something bedevils you, it's like having a pesky opponent who keeps finding new ways to cause problems. A chef might be bedeviled by a recipe that never turns out quite right, or a detective might be bedeviled by a case with too many confusing clues.

Notice that bedevil suggests the trouble is both persistent and somewhat mysterious. You face an unclear obstacle you cannot simply remove: you're dealing with something slippery and stubborn that keeps coming back.