net having the sense of hearing; deaf.-unheard.-involving surds; not capable of being expressed in rational numbers; radical; irrational; as, a surd expression or quantity; a surd number.-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.-a quantity which can not be expressed by rational numbers; thus, ã2 is a surd.-a surd element of speech. see surd, a., 4.