Sentence:  The Houses may meet in <WSD>extraordinary</WSD> sessions at the request of the Government, of the Permanent Deputation or of the overall majority of members of either of the two Houses. <WSD>Extraordinary</WSD> sessions must be convened with a specific agenda and shall be adjourned once this has been dealt with. 
Meaning of the word marked with <WSD> tags:  Not ordinary; exceptional; unusual.