Definition of surds:
(n) :
(arithmetic) An irrational number, especially one expressed using the √ symbol.
(adj) :
(mathematics) Involving surds, or irrational numbers; not capable of being expressed in rational numbers.
(n) :
(linguistics) A voiceless consonant.
(adj) :
(phonetics) unvoiced; voiceless
(adj) :
(obsolete) Lacking the sense of hearing; deaf.
(adj) :
(obsolete) unheard