Abysmal means extremely bad or terrible, so poor that it seems bottomless. When your performance on a math test is abysmal, you did spectacularly badly, maybe getting only two questions right out of twenty. When the weather is abysmal, it might be storming with thunder, lightning, and flooding all at once.

When something is abysmal, it's as if it has fallen into a dark chasm with no bottom in sight. A team might have an abysmal season, losing almost every game. A restaurant might receive abysmal reviews if the food is cold, the service is slow, and the place is dirty.

Notice that abysmal is stronger than just “bad.” You wouldn't say your pretty good day was abysmal just because you forgot your lunch. Save this word for situations that are truly, deeply, spectacularly awful. The word carries weight, describing conditions or results that hit rock bottom.