The Collaborative International Dictionary of English v.0.48:

Cuckold \Cuck"old\ (k?k"?ld), n. [OE. kukeweld, cokewold,
   cokold, fr. OF. coucoul, cucuault, the last syllable being
   modified by the OE. suffix -wold (see Herald); cf. F. cocu
   a cuckold, formerly also, a cuckoo, and L. cuculus a cuckoo.
   The word alludes to the habit of the female cuckoo, who lays
   her eggs in the nests of other birds, to be hatched by them.]
   1. A man whose wife is unfaithful; the husband of an
      adulteress. --Shak.
      [1913 Webster]

   2. (Zool.)
      (a) A West Indian plectognath fish (Ostracion
          triqueter).
      (b) The cowfish.
          [1913 Webster]