afoul

To run afoul of something is to come into conflict with it or get tangled up in a difficult situation. Originally a nautical term for a ship colliding with another vessel—or for lines and anchors becoming tangled—it has sailed into everyday language to describe less literal collisions. Today, you are most likely to hear it when someone breaks a rule; for example, a company might run afoul of environmental laws. It implies a state of entanglement or collision with an opposing force.

Afoul describes a state of collision, entanglement, or conflict. While it can mean that a plan has gone wrong (similar to "amiss"), it is most frequently used in the idiom "to run afoul of" (and sometimes "to come/go afoul of"). These phrases suggest colliding with established rules, standards, or authorities. For instance: "The startup ran afoul of complex tax regulations," or "He tried to be helpful but eventually ran afoul of the manager."

The word implies a physical or metaphorical snarl. A fishing line might run afoul of weeds or rocks, just as a politician might run afoul of public opinion. In both cases, forward motion is stopped by an obstruction.

The term is historically nautical. A ship was said to be "afoul" if it crashed into another vessel or if its anchors and lines became hopelessly twisted. That sense of a messy, dangerous, and unintentional connection remains in the word today. Unlike a simple mistake, going afoul suggests you have been ensnared by the consequences of an event or action.