The Collaborative International Dictionary of English v.0.48:

Yid \Yid\, n. [See Yiddish.]
   A Jew; -- now (1998) usually considered offensive or
   contemptuous. [Slang or Colloq.] "Almost any young Yid who
   goes out from among her people." --John Corbin.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

yid
    n 1: (ethnic slur) offensive term for a Jew [syn: kike,
         hymie, sheeny, yid]