surd

plural surds

1. arithmeticAn irrational number, especially one expressed using the √ symbol.
2. human sciencesA voiceless consonant.

   Antonyms: sonant

comparative more surd · superlative most surd

1. obsoleteLacking the sense of hearing; deaf.

   …how all Words fall to the Ground, spent upon such a surd and Earless Generation of Men, stupid unto all Instruction…

   1670s, published 1716, Thomas Browne, Christian Morals, part 3, section 6

2. obsoleteunheard

   To this errour, of blending the ſurd and vocal modes of articulation together, may be added the too frequent uſe of compound articulations both vocal and ſurd.

   1773, William Kenrick, A New Dictionary of the English Language, section 3, page 5

3. mathematicsInvolving surds, or irrational numbers; not capable of being expressed in rational numbers.

   a surd expression or quantity; a surd number

4. human sciencesunvoiced; voiceless

   Antonyms: sonant