It is a term used as a simile for the unseen yet consequential barrier that prevents a certain set of individuals from ascending hierarchy, especially in the corporate sense, irrespective of their qualification or contribution. The term was coined in the context of feminism, but is now used in the context of minorities too.
Four conditions constituting evidence of a glass ceiling have been identified. The difference (in gender, race or other characteristic) must not be explicable in terms of job-relevant characteristics, it must affect opportunities afforded for advancement rather than merely current proportions, it must be greater at higher levels than at lower levels of outcome, and it must be one that increases over the course of the career.
Causes of the continuing existence of the glass ceiling are pointed out as not only the maintenance of stereotypes and/or prejudice but also because women are relatively under-represented in STEM fields to begin with, have fewer role models and may limit their own ambitions.