En`tre·sol' noun [ French] (Architecture) A low story between two higher ones, usually between the ground floor and the first story; mezzanine. Parker. Found on http://www.encyclo.co.uk/webster/E/50
In architecture an entresol is a low story between two higher ones, usually between the ground floor and the first story, like a mezzanine. Found on http://www.probertencyclopaedia.com/browse/TE.HTM