Dictionary.net

• a person who is important by virtue of the people or votes they control; "a power broker who does you a favor will expect you to return it"

2006 - WordNet 3.0
By Princeton University

• a person who is important by virtue of the people or votes they control; "a power broker who does you a favor will expect you to return it"

2011 - English Dictionary Database
By DataStellar Co., Ltd