To register for higher education, or as an ornate way of referring to one’s time therein
He matriculated at Rostock, where he found little astronomy but a good deal of astrology.
— Walter William Bryant, Kepler (1920)
The peak of my school experience of Shakespeare came in my senior matriculation year; the set play was “A Midsummer Night’s Dream”, and it was taught by a solemn donkey who understood nothing but the political organization of fairyland.
— Robertson Davies, Shakespeare over the Port (1960)
Congratulations lad, you’re a fully matriculated student at State University.
— Colonel Gathers, The Venture Brothers
Latin, ultimately from the same source as “mater” (mother), like “alma mater”, your bountiful mother school.