Is there a conventional word that describes a professor for whom you were a TA
I would initially suggest terms supervising lecturer or supervising teaching professor. However, both terms are not perfect due to potential interpretation of "lecturer" and "teaching professor" as formal positions. In order to improve this, it might make sense to add clarifying term "class" and remove "teaching" from the second option. Therefore, my final suggestions are the following two options:


supervising class (course) lecturer;
supervising class (course) professor.