sea pen

American  

noun

1. any of several colonial coelenterates of the genus Pennatula and related genera, having the shape of a fleshy feather.

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sea pen British  

noun

1. any of various anthozoan coelenterates of the genus Pennatula and related genera, forming fleshy feather-like colonies in warm seas: order Pennatulacea

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Etymology

Origin of sea pen

First recorded in 1755–65

Example Sentences

This makes it well-adapted to hide within the white leaves of its sea pen host.

From Science Daily • Oct. 8, 2025

A small creature called a sea pen, which helps to build reefs, could lose up to 40% of their suitable habitat by the end of the century.

From BBC • Jun. 17, 2025

The Dolphin Company, based in Mexico, had agreed to help move Lolita to a natural sea pen in the Pacific Northwest when it took over ownership of the Seaquarium in 2022.

From Seattle Times • Mar. 7, 2024

They demanded that SeaWorld cease capture operations within state waters; eventually, the case was settled out of court, with SeaWorld releasing the just-captured orcas from their sea pen and agreeing not to return.

From Salon • Apr. 6, 2014

Keiko had been rescued from a theme park in Mexico and released into a sea pen, only to later die from pneumonia.

From National Geographic