General synonyms:
* Conversation
* Talk
* Discussion
* Discourse
* Interchange
* Communication
* Chat
* Rap
* Parley
* Colloquy
More specific synonyms:
* Debate: When dialogue involves arguing or differing viewpoints.
* Negotiation: When dialogue focuses on reaching an agreement.
* Conference: A formal dialogue between two or more parties.
* Conversation: A casual and informal exchange of ideas.
* Chat: A light and friendly conversation.
The best synonym for "dialogue" depends on the specific situation and what you're trying to convey.