Surd (?), a. [L. surdus deaf (whence the meaning, deaf to reason, irrational), perhaps akin to E. swart. Cf. Sordine.]
1.
Not having the sense of hearing; deaf.
[Obs.] "A
surd . . . generation."
Sir T. Browne.
2.
Unheard.
[Obs.]
Kenrick.
3. Math.
Involving surds; not capable of being expressed in rational numbers; radical; irrational; as, a surd expression or quantity; a surd number.
4. 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.
© Webster 1913.
Surd, n. Math.
1.
A quantity which can not be expressed by rational numbers; thus, √2 is a surd.
2. Phon.
A surd element of speech. See Surd, a., 4.
© Webster 1913.