# nautilus

/ˈnɔtəɫəs/ (US) · /nˈɔːtɪləs/ (UK) · CEFR C1 · Noun

Source: https://englishreference.com/word/nautilus
Updated: 2026-05-20

## Definition

a large, sea-dwelling animal with a shell that looks like a spiral. It is related to the chambered nautilus and is often called a 'sea horse' in some parts of the world.

For teachers: a marine mollusk of the family Nautilidae, characterized by a chambered, spiral shell. Often referred to as a 'sea horse' in certain regional dialects.

## Examples

- The nautilus swims slowly through the deep ocean.
- Divers often spot a nautilus near the coral reefs, where it uses its shell to control its buoyancy.
- The nautilus is one of the few living species that has remained largely unchanged for millions of years, making it a living fossil in the world of marine biology.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.