Compersion: The word compersion describes the feeling of being happy, turned on, or excited about the idea of your partner being happy, romantically or sexually, with another person. Polysaturated: A term for when a person is polyamorous but not currently open to new partners or relationships. This doesn't mean that they all have to be dating each other.
Polycule: A polycule is the group of all the people who are somehow connected through the romantic relationships they are in. Metamours may or may not interact with each other, depending on the structure of the relationship.
Metamour: This is your partner's partner. This means that whoever is involved in this relationship is in the know and agrees to the relationship dynamics.
Ethical non-monogamy: This is the umbrella term for consensual relationships where people agree to have more than one romantic or intimate relationship at a time.