[verb uhn-der-lahyn, uhn-der-lahyn; noun uhn-der-lahyn]
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verb (used with object), un·der·lined, un·der·lin·ing.
  1. to mark with a line or lines underneath; underscore.
  2. to indicate the importance of; emphasize, as by stressing or italicizing.
  1. Printing. a caption under an illustration.
  2. a line drawn under something; an underscore.

Origin of underline

First recorded in 1715–25; under- + line1
Related formsun·der·lin·ing, un·der·lin·e·a·tion [uhn-der-lin-ee-ey-shuh n] /ˌʌn dərˌlɪn iˈeɪ ʃən/, nounun·der·lin·er, noun
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

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British Dictionary definitions for underlining


verb (ˌʌndəˈlaɪn) (tr)
  1. to put a line under
  2. to state forcibly; emphasize or reinforce
noun (ˈʌndəˌlaɪn)
  1. a line underneath, esp under written matter
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

Word Origin and History for underlining



1721, from under + line (v.). Cf. Dutch onderlijnen. Related: Underlined; underlining. The noun is attested from 1888.

Online Etymology Dictionary, © 2010 Douglas Harper