1700, Charles Hopkins, The Art of Love, (after Ovid’s Ars Amatoria), London: Joseph Wild, “The Muse,” p. 36,
At first, perhaps, unread your Note’s return’d,
Your Person slighted, and your Passion scorn’d.
The book I got for my 18th birthday remained unread until my retirement.
Not having read; uneducated.
1796, Elizabeth Inchbald, Nature and Art, Dublin: P. Wogan et al., Chapter 22, p. 111,
The only child of two doating parents, she never had been taught the necessity of resignation—untutored, unread, unused to reflect, but knowing how to feel […]
1890, Frances Willard, Address before the Seventeenth Convention of the World Woman’s Christian Temperance Union at Atlanta, Georgia, in William Jennings Bryan (editor), The World’s Famous Orations, New York: Funk & Wagnalls, 1906, Volume 10, p. 162,
[…] only those unread in the biography of genius imagine themselves to be original.
verb
(transitive) To undo the process of reading.
That book was terrible! I wish I could unread it.
(computing, transitive) To flag (a previously read e-mail or similar message) as not having been read.