WordNet (r) 3.0 (2006):

House of Commons
    n 1: the lower house of the British parliament [syn: House of
         Commons, British House of Commons]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

HOUSE OF COMMONS, Eng. law. The representatives of the people, in
contradistinction to the nobles, taken collectively are called the house of
commons.
     2. This house must give its consent to all bills before they acquire
the authority of law, and all laws for raising revenue must originate there.