Source : Webster's Revised Unabridged Dictionary (1913)

Exon \Ex"on\, n. [NL., from E. Exe (Celt. uisge water) the name
   of a river.]
   A native or inhabitant of Exeter, in England.

Exon \Ex"on\, n. [F. expect an under officer.]
   An officer of the Yeomen of the Guard; an Exempt. [Eng.]

Source : WordNet®

exon
     n : sequence of a gene's DNA that transcribes into protein
         structures; "exons are interspersed with introns" [syn: {coding
         DNA}] [ant: {intron}]