The Collaborative International Dictionary of English v.0.48:

Whoreson \Whore"son\, n.
   A bastard; colloquially, a low, scurvy fellow; -- used
   generally in contempt, or in coarse humor. Also used
   adjectively. [Archaic] --Shak.
   [1913 Webster]

WordNet (r) 3.0 (2006):

whoreson
    n 1: the illegitimate offspring of unmarried parents [syn:
         bastard, by-blow, love child, illegitimate child,
         illegitimate, whoreson]
    2: insulting terms of address for people who are stupid or
       irritating or ridiculous [syn: asshole, bastard,
       cocksucker, dickhead, shit, mother fucker,
       motherfucker, prick, whoreson, son of a bitch, SOB]