What do we mean when we talk about ‘selective’ universities?

Edward Peck:

Adopting language already in common use elsewhere, the Office for Fair Access (OFFA) has taken to calling those universities who admit the fewest students from low-income households the ‘selective’ universities. But what does ‘selective’ mean in this context?

Is it accurate to apply the term only to those higher education institutions admitting more privileged students? What does it do to the broader perception – and perhaps, more importantly, the self-perception – of those students from poorer backgrounds when it is implied that they are not attending a ‘selective’ university? In the context of the recent Green Paper, where do the best prospects of driving social mobility lie?