The term glass ceiling is a political term often used to describe an unbreakable barrier that is not visible with the human eye, but it keeps minorities from rising up i.e. it is a barrier to minority groups, in the past (and sometimes still) for women, that stops them from achieving their true potential.
FrancisQ.C. R.2013Report of the Mid Staffordshire NHS Foundation Trust Public Inquiry [online] Available from: http://www.midstaffspublicinquiry.com/report [Accessed October 2015] (7) 245–8