DuckCorp Dico

Found one definition

1.                 From WordNet (r) 3.0 (2006):
                   
   
   
                   
                     
   surd
       adj 1: produced without vibration of the vocal cords; "unvoiced
              consonants such as `p' and `k' and `s'" [syn: unvoiced,
              voiceless, surd, hard] [ant: soft, sonant,
              voiced]
       n 1: a consonant produced without sound from the vocal cords
            [syn: surd, voiceless consonant]