Surd /(?)/

Surd

a.
  1. Net having the sense of hearing; deaf. [Obs.]
  2. Unheard. [Obs.]
  3. Involving surds; not capable of being expressed in rational numbers; radical; irrational; as, a surd expression or quantity; a surd number. (Math.)
  4. 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. (Phonetics)

Surd

n.
  1. A quantity which can not be expressed by rational numbers; thus, √2 is a surd. (Math.)
  2. A surd element of speech. See Surd, a., 4. (Phon.)