"He dove into the abyss" is a sentence that demonstrates correct usage of the word "abyss." The word is a noun that refers to a vast chasm or cavity of immeasurable and remarkable depth.
The word "abyss" has further denotations; it also refers to anything that has a profoundly unfathomable or infinite quality, such as time or space. The word can also be used in a sentence such as "the abyss of time has fascinated philosophers and scientists for centuries." In yet another denotation, the word indicates an infernal region or hell. The word comes from the Latin "abyssus," which refers to a bottomless pit and in turn comes from the Greek "abyssos."