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1. Net having the sense of hearing; deaf. A surd . . . Generation.

2. Unheard.

3. (Science: mathematics) Involving surds; not capable of being expressed in rational numbers; radical; irrational; as, a surd expression or quantity; a surd number.

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.

Origin: L. Surdus deaf (whence the meaning, deaf to reason, irrational), perhaps akin to E. Swart. Cf. Sordine.

(Science: mathematics)

1. A quantity which can not be expressed by rational numbers; thus, 2 is a surd.

2. A surd element of speech. See Surd.