"By a hair" is an idiom commonly used to describe a situation where something almost didn't happen or barely happened. Its antonyms include "by a mile," which means something was easily achieved or accomplished, and "by a long shot," which means something was nowhere near happening or being accomplished. Another antonym is "by a landslide," which is used to describe a situation when something overwhelmingly won. It is important to understand the different meanings of these idioms, as their incorrect usage can cause confusion and miscommunication. So the next time you want to express how close or far something was, remember the different antonyms for "by a hair.