Abbreviation of a private university (run by a non-governmental institution), as opposed to national or public universities.
私は来年、私大に進学する予定です。
I'm planning to enter a private university next year.
私大は授業料が高いことが多い。
Private universities often have high tuition fees.
彼は私大の経済学部で勉強している。
He studies in the economics faculty of a private university.