The phrase "imagined speech" can have different synonyms depending on the context. If the speech is meant to be a fictional or hypothetical dialogue between characters, some synonyms can be "dialogue," "conversation," or "fictional discourse." If the speech is being used in the context of mental health or psychology, some synonyms can be "internal dialogue," "self-talk," or "imaginary conversation." In the field of literature, "monologue," "soliloquy," or "stream of consciousness" can be used as synonyms. Overall, the synonyms for "imagined speech" will depend on the specific context in which it is being used.