Wordnet 3.0
NOUN (1)
1. 
 a major social class or order of persons regarded collectively as part of the body politic of the country (especially in the United Kingdom) and formerly possessing distinct political rights; 
[syn: estate of the realm, estate, the three estates]
WordNet (r) 3.0 (2006):
estate of the realm
    n 1: a major social class or order of persons regarded
         collectively as part of the body politic of the country
         (especially in the United Kingdom) and formerly possessing
         distinct political rights [syn: estate of the realm,
         estate, the three estates]