Surd
Surd , adjective
[Latin surdus deaf (whence the meaning, deaf to reason, irrational), perhaps akin to English swart. Compare Sordine.]
1.
Net having the sense of hearing; deaf. [Obsolete]
A surd... generation.
2.
Unheard. [Obsolete] — Kenrick
3.
(Mathematics) 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.
Surd , noun
1.
(Mathematics) A quantity which can not be expressed by rational numbers; thus, r2 is a surd.
2.
(Phonetics) A surd element of speech. See Surd, a., 4.