Search Result for "expert witness":
Wordnet 3.0

NOUN (1)

1. a witness who has knowledge not normally possessed by the average person concerning the topic that he is to testify about; 



WordNet (r) 3.0 (2006):

expert witness
    n 1: a witness who has knowledge not normally possessed by the
         average person concerning the topic that he is to testify
         about [ant: lay witness]