from The American Heritage® Dictionary of the English Language, 5th Edition.

  • noun Mathematics An irrational number, such as √2.
  • noun Linguistics A voiceless sound in speech.
  • adjective Voiceless, as a sound.

from The Century Dictionary.

  • To render dim or soft; mute.
  • Containing or involving a surd : thus [1 + ½] ½ is a surd expression but not a surd, since 1 + ½ is not a rational expression.
  • noun In mathematics: An indicated root whose value is irrational, but whose radicand is rational, as ½. A surd is quadratic, cubic, of order n, according as its exponent is ½, ⅓, 1/n;.
  • Not having the sense of hearing; deaf.
  • That cannot be discriminated by the ear (?).
  • In mathematics, not capable of being expressed in rational numbers: as, a surd expression, quantity, or number. See II., 1.
  • In phonetics, uttered with breath and not with voice; devoid of vocality; not sonant: toneless: specifically applied to the breathed or non-vocal consonants of the alphabet. See II., 2.
  • Meaningless; senseless.
  • noun In mathematics, a quantity not expressible as the ratio of two whole numbers, as √ 2, or the ratio of the circumference of a circle to the diameter.
  • noun In phonetics, a consonantal sound uttered with breath and not with voice; a non-sonant consonant; a non-vocal alphabetic utterance, as p, f, s, t, k, as opposed to b, v, z, d, g, which are sonants or vocals.

from the GNU version of the Collaborative International Dictionary of English.

  • noun (Math.) A quantity which can not be expressed by rational numbers.
  • noun (Phon.) A surd element of speech. See Surd, a., 4.
  • adjective obsolete Net having the sense of hearing; deaf.
  • adjective obsolete Unheard.
  • adjective (Math.) Involving surds; not capable of being expressed in rational numbers; radical; irrational.
  • adjective (Phonetics) Uttered, as an element of speech, without tone, or proper vocal sound; voiceless; unintonated; nonvocal; atonic; whispered; aspirated; sharp; hard, as f, p, s, etc.; -- opposed to sonant. See Guide to Pronunciation, §§169, 179, 180.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • noun arithmetic An irrational number, especially one expressed using the √ symbol.
  • noun linguistics A voiceless consonant.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • noun a consonant produced without sound from the vocal cords
  • adjective produced without vibration of the vocal cords


from The American Heritage® Dictionary of the English Language, 4th Edition

[Medieval Latin surdus, speechless, surd (translation of Arabic (jaḏr) ’aṣamm, deaf (root), surd, translation of Greek alogos, speechless, surd), from Latin.]


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  • Jeremy Piven winning an Emmy three years in a row for that role, is up surd.

    Entourage Renewed For Sixth Season | /Film 2008

  • So even though she may find her own action inexplicable or “surd,” she is in fact acting rationally, although she does not know it.

    Weakness of Will Stroud, Sarah 2008

  • Must it needs be, that a daughter of the same father and mother must be more silly, more unsteady, more ab-surd, more impertinent, than her brother?

    Sir Charles Grandison 2006

  • Or, rather of what ab-surd things does it make its votaries guilty?

    Sir Charles Grandison 2006

  • County Monachan, whereat samething is rivi-sible by nighttim, may be involted into the zeroic couplet, palls pell inhis heventh glike noughty times ì, find, if you are not literally cooefficient, how minney combinaisies and per-mutandies can be played on the international surd! pthwndxrclzp!, hids cubid rute being extructed, taking anan illitterettes, ififif at a tom.

    Finnegans Wake 2006

  • Do you mean to say that you are not able to tell me what a surd is?

    A Portrait of the Artist as a Young Man 2003

  • Hence, as in Augustine, there is no intrinsic or surd evil; evil is justified as the means of developing man from bondage to self-conscious participation in the


  • [4] For 'voiceless,' 'surd,' 'hard,' or 'tenuis' are sometimes used.

    New Latin Grammar Charles E. Bennett

  • Coercion is the surd in almost all social theory, except the

    Public Opinion Walter Lippmann 1931

  • Do you mean to say that you are not able to tell me what a surd is?

    A Portrait of the Artist as a Young Man Joyce, James, 1882-1941 1922


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  • an irrational number, that is, one which cannot be written as the quotient of two integers

    November 16, 2007

  • With a simple explanation they are no longer absurd.

    November 16, 2007

  • "The organic law of vegetable growth is the surd towards which the series one-half, one-third, two-fifths, three-eighths, and so one, approximates." "Fifty-seven Views of Fujiyama" by Guy Davenport

    January 19, 2010

  • The Latin surdus gave rise to sordino in Italian and sourdine in French, both meaning mute, the device that modifies the sound produced by musical instruments, especially in jazz.

    March 14, 2013

  • The number expressing the golden section is a surd, as commented on by jaime_d.

    March 14, 2013

  • ad+surd?

    March 14, 2013

  • I got into a fight after playing this word in scrabble once.

    March 14, 2013

  • That's why I don't play scrabble, I can't afford the helmet and protective vest.

    March 14, 2013

  • 3-14-13 pisurd - silence please- (it should be 3.1415...) totally real number as in 'pi''ve got your number'?

    In Berkeley's forest, no one herd this rite!

    What a daunting spell-(rite) has been cast!

    March 15, 2013

  • "His voice was certainly the strangest I've heard from a creature of his kind-- at once surd and resonant, clipped and lyrical, with euphonious vowels broken by brusquely stressed consonants that reminded me a little of Careclough's Scottish brogue."

    The No Variations by Luis Chitarroni, translated by Darren Koolman, p 114

    September 16, 2013