Definition of surd

• a. - Net having the sense of hearing; deaf.
• a. - Unheard.
• a. - Involving surds; not capable of being expressed in rational numbers; radical; irrational; as, a surd expression or quantity; a surd number.
• a. - 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.
• n. - A quantity which can not be expressed by rational numbers; thus, Ã2 is a surd.
• n. - A surd element of speech. See Surd, a., 4.