| Word | Definitions | Synonyms |
|---|---|---|
| abyss | (noun) a bottomless gulf or pit; any unfathomable (or apparently unfathomable) cavity or chasm or void extending below (often used figuratively) | Synonyms: abysm |
| byssus | (noun) tuft of strong filaments by which e.g. a mussel makes itself fast to a fixed surface | Synonyms: beard |