noun ·Rare ·Advanced level

Definitions

Noun

1. 1
   That part of the Earth, or other planet, that lies below the surface of its lakes, seas and oceans, countable, uncountable

Synonyms

All synonyms

hydrospherehydrosphere

Etymology

From hydro- + space.

Data sourced from Wiktionary, WordNet, CMU, and other open linguistic databases. Updated March 2026.