noun
auditor; auditing student
A student who attends a course without receiving official credit or a degree; common in university settings.
彼は聴講生として大学の授業に参加している。
He is attending university classes as an auditing student.
A student who takes individual courses for credit, unlike 聴講生 who audits without credit.
Compound of 聴講 (chōkō, 'attending a lecture') + 生 (sei, 'student').