“Unicorn” describes a person who joins a couple as their third partner, for sex or even for something more committed. Even in conversation, it felt good to be someone who could fulfill not just one persons fantasy, but two at once.

What does it mean to be someones unicorn?

Typically a sex unicorn is a bisexual woman who agrees to join a pre-existing heterosexual marriage as a third sexual component, without presenting any threat of infidelity or emotional burden to either the husband or wife.