pi·​ne·​al | \ ˈpī-nē-əl How to pronounce pineal (audio) , pī-ˈnē- How to pronounce pineal (audio) \

Definition of pineal

: of, relating to, or secreted by the pineal gland a pineal tumor the pineal hormone melatonin

Examples of pineal in a Sentence

Recent Examples on the Web This video shows a monitor lizard skull fossil fragment with both the parietal and pineal foramina visible (highlighted in yellow). Amina Khan,, "If two eyes are good, four were even better for this lizard species," 3 Apr. 2018 What purpose the fourth eye served in addition to pineal eye is hard to say. David Grossman, Popular Mechanics, "An Ancient Lizard Had Four Eyes But We Don't Know Why," 2 Apr. 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'pineal.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

First Known Use of pineal

1681, in the meaning defined above

History and Etymology for pineal

French pinéal, from Middle French, from Latin pinea pine cone, from feminine of pineus of pine, from pinus

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Time Traveler for pineal

Time Traveler

The first known use of pineal was in 1681

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Cite this Entry

“Pineal.” Dictionary, Merriam-Webster, Accessed 12 Jul. 2020.

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More Definitions for pineal


pi·​ne·​al | \ ˈpī-nē-əl How to pronounce pineal (audio) , pī-ˈ How to pronounce pineal (audio) \

Medical Definition of pineal

 (Entry 1 of 2)

: of, relating to, or being the pineal gland



Medical Definition of pineal (Entry 2 of 2)

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