Fourth year UNSW honours student Sean Lynch said his lecturer did not want to use the term "marriage" when referring to a theory proved by English mathematician Phillip Hall in 1935.
A lecturer is reported to have asked students not to use the word "marriage" in Hall's Marriage Theorem when using the longstanding example of pairing a number of men and women to represent different variable sets.
"In that course it was communicated to me that Hall's marriage theorem was offensive," Mr Lynch claimed on Sky News.
"That lecturer advised that we not refer to the theorem by that name in the assignment."
"The reason why was because the canonical example has homophobic implications, at least in her eyes,' he added.
Mr Lynch, the founder of the UNSW student group Free Thinkers, said the response was "unjustified", but he was concerned about speaking out because people are becoming so "riled up" over marriage equality.
A UNSW spokesperson said there were concerns within the mathematical community the theory would isolate some groups, but have reached out to the students to address concerns.
"The concern in the UNSW mathematical community was that the traditional narrative for presenting Hall's Theorem - sometimes known as the Marriage Theorem - might isolate some groups,' a spokesperson told SBS World News.
"We understand that this suggestion has upset some students and we are in contact with the students involved to address their concerns."
Mr Lynch said same-sex marriage was never specifically mentioned in the comments from the lecturer.
Sean Lynch holds no bad feelings towards the department and hopes to possibly move into academia in the future.
Another student was reportedly given similar written feedback when they had their assignment marked by a staff member.