a fluid for producing writing that is invisible until brought out by heat, chemicals, etc.
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How to use invisible ink in a sentence
Last two words are written in invisible ink but can be easily discerned if Australian law books are held over scented candles.Up to a Point: 2013 in Review and Predictions for 2014 | P. J. O’Rourke | January 1, 2014 | THE DAILY BEAST
He communicated invisible ink on postcards, and a special code of microdots.Second ‘Underwear Bomber,’ Kim Philby, and Other Notorious Double Agents | The Daily Beast | May 10, 2012 | THE DAILY BEAST
invisible ink makes an appearance in the complaint as does Morse Code, which, of course, is pretty uncrackable.
We always write our most secret doings in invisible ink, made of lemon juice, so that nobody can read about them.The Boy Scouts of Bob's Hill | Charles Pierce Burton
Dip the roses in the red invisible ink, the jonquilles in the yellow, the pinks in the violet, and the leaves in the green ink.Endless Amusement | Unknown
Here for some reason the invisible ink answered less reluctantly to the warmth of the blue flames' invitation.The Messenger | Elizabeth Robins
Our censor chaps at home have got to be quite expert at reading letters, invisible ink and all that sort of thing.The Apartment Next Door | William Andrew Johnston
By writing in newspapers, sometimes with invisible ink or by enclosing accounts or letters in them.The History of the British Post Office | Joseph Clarence Hemmeon
British Dictionary definitions for invisible ink
a liquid used for writing that does not become visible until it has been treated with chemicals, heat, ultraviolet light, etc
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012