grey area

noun

(in Britain) a region in which unemployment is relatively high
an area or part of something existing between two extremes and having mixed characteristics of both
an area, situation, etc, lacking clearly defined characteristics
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012