Translation:Marcus and Stephanus have a conversation.
It occurs only a few times among the ancient authors, and as far as I can see always in the context of army leaders having formal parleys or negotiations over war and peace.
I would not advise using this to mean something like "have a chat", as it seems to be being used here. Probably better to think of it as "to parley", "to enter into discussion", "to engage in negotiations".
Agree with the bad Duo translation here, and the meaning you give, but not always for war: Gaffiot gives different contexts. Not always war, but something like parleys/negotiations (with the meaning of a "speaking" meeting)/a talk between several persons, for anything (not related to war).