According to Wikipedia:
"A multilateral NDA involves three or more parties where at least one of the parties anticipates disclosing information to the other parties and requires that the information be protected from further disclosure. This type of NDA eliminates the need for separate unilateral or bilateral NDAs between only two parties. e.g; a single multiparty NDA entered into by three parties who each intend to disclose information to the other two parties could be used in place of three separate bilateral NDAs between the first and second parties, second and third parties, and third and first parties.
A multilateral NDA can be advantageous because the parties involved review, execute, and implement just one agreement. However, this advantage can be offset by more complex negotiations that may be required for the parties involved to reach a unanimous consensus on a multilateral agreement."