The communication management plan is the written document that outlines, highlights, and details the communications needs and expectations for the entire project. This can include specific communications technologies that are required, such as need for dedicated cell phones so that the project team members can keep in touch, as well as specific update formats, such as the need for a weekly email update, or perhaps the need for a weekly conference call.
The communication management plan also includes mention of the specific party or parties who are to be responsible for each format of communication. Communication management plans come in a wide variety of shapes and sizes. Some can be formally written, others can be more informal drafts. They can be extremely detailed, or can be written very broadly, meant more to steer project team members in a general direction (i.e., “Send the team a weekly email to update) as opposed to providing specific rigid instruction (i.e., “Send a weekly email to these specific members on this specific day to update).
This term is defined in the 3rd and the 4th edition of the PMBOK.