A student who studies abroad for a fixed period under an exchange agreement between institutions.
An exchange student from the US is coming next month.
He went to Japan as an exchange student when he was in high school.
留学生 is the general term for any student studying abroad, while 交換留学生 specifically refers to a student on a reciprocal exchange program.
Compound of 交換 (exchange) + 留学生 (international student).