collocutor
Concise Oxford English Dictionary © 2008 Oxford University Press:
collocutor /ˈkɒləˌkjuːtə, kəˈlɒkjʊtə/
▶noun rare a person who converses with another.
– origin C16: from late L., from collocut-, colloqui ‘to converse’.
'collocutor' also found in these Oxford entries:

