Polyamory , also known as polyphilia or multiamory, is the practice, desire, or acceptance of having more than one intimate relationship at a time with the knowledge and consent of everyone involved.
Polyamory, often abbreviated to poly, is sometimes described as consensual, ethical, or responsible non-monogamy. The word is occasionally used more broadly to refer to any sexual or romantic relationships that are not sexually exclusive, though there is disagreement on how broadly it applies; an emphasis on ethics, honesty, and transparency all around is widely regarded as the crucial defining characteristic.
"Polyamorous" can refer to the nature of a relationship at a given time, or be used as a description of a philosophy or relationship orientation , rather than a person's actual relationship status at a given moment. It is an umbrella term that covers various forms of multiple relationships; polyamorous arrangements are varied, reflecting the choices and philosophies of the individuals involved.
Wikipedia, Polyamory, http://en.wikipedia.org/wiki/Polyamory (as of Apr 1, 2010)