SURD, adjective [Latin surdus, deaf.] Deaf; not having the sense of hearing. [Not used.] 1. Upheard. [Not used.] 2. Designating a quantity whose root cannot be exactly expressed in numbers. SURD, noun In algebra, a quantity whose root cannot be exactly expressed in numbers. Thus 2 is a surd number, because there is no number which multiplied into itself, will exactly produce 2.
Source: Webster's 1828 American Dictionary ↗ · public-domain · returned verbatim, no AI