# pneumatocyst

> English word · Noun

## Definitions
1. A sac or other structure containing air and used for flotation by a marine organism, chiefly used in reference to those of kelps and siphonophores.

## Etymology
From pneumato- + cyst.

## Source
Compiled from Wiktionary via kaikki.org (CC BY-SA). Data vintage: 2026-05-06.
Canonical page: https://plainspell.com/en/word/pneumatocyst