invisible ink

American  

[in-viz-uh-buhl ingk] / ɪnˈvɪz ə bəl ˈɪŋk /

noun

1. a fluid for producing writing that is invisible until brought out by heat, chemicals, etc.

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invisible ink British  

noun

1. a liquid used for writing that does not become visible until it has been treated with chemicals, heat, ultraviolet light, etc

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Etymology

Origin of invisible ink

First recorded in 1675–85

Example Sentences

See Examples For:

invisible ink

Then the justices pitch a fit when the courts below don’t understand how to apply these orders written in invisible ink.

From Slate ● Oct. 20, 2025

In another, attributed to Aeneas the Tactician, a message hides dots of invisible ink over certain letters, which spell out the true message.

From Scientific American ● Jun. 15, 2023

Whether she's aware of the passages written in invisible ink in the margins and paragraph breaks is not for me to know or decode for my entertainment.

From Salon ● Feb. 26, 2023

Lydia Tár exists as if on a folded-over page in that world, where the correct answer to the perennially misunderstood question about the distinction between art and life is written in invisible ink.

From New York Times ● Jan. 2, 2023

Each match was actually a pen that wrote with invisible ink.

From Nazi Saboteurs by Samantha Seiple