Some reference works define polyamory as a relational form (whether interpersonal or romantic or sexual) that involves multiple people with the consent of all the people involved, like Oxford Living Dictionaries, Cambridge Advanced Learner's Dictionary and Thesaurus, and Dictionary.com.

Polyamory is a relatively new word, coined around 1990 by Morning Glory Ravenheart Zell, that has Latin and Greek roots that translate to “loving many.” There is no single definition of polyamory, and many people use the word to mean different things.

the practice of having sexual or romantic relationships with two or more people at the same time: For him, polyamory is more honest and natural than monogamy.