The Collaborative International Dictionary of English v.0.48:

Baronage \Bar"on*age\, n. [OE. barnage, baronage, OF. barnage,
   F. baronnage; cf. LL. baronagium.]
   [1913 Webster]
   1. The whole body of barons or peers.
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            The baronage of the kingdom.          --Bp. Burnet.
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   2. The dignity or rank of a baron.
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   3. The land which gives title to a baron. [Obs.]
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WordNet (r) 3.0 (2006):

baronage
    n 1: the peers of a kingdom considered as a group [syn:
         peerage, baronage]