significant other

plural significant others

1. One's exclusive romantic partner.

   More than half (57 percent) of consumers think it would be wonderfully romantic if their significant other booked tickets for a surprise international trip.

   2006 February 12, Michelle Singletary, “Love and money go hand in hand”, in Boston Globe, retrieved 27 Oct 2013

   1 more example

   Almost half of working women who are married or live with a partner are seeing their significant other only in passing because the two work different shifts, an AFL-CIO poll found.

   2000 March 9, “Couples Working Different Shifts, Union Poll Finds”, in Deseret News, retrieved 27 Oct 2013, page D7

   Synonyms: better half, other half, partner, s/o, SO

2. A person with whom one has an important bond of some kind.

   Dr. Nogueira said it was always preferable to have coaches drawn from a school's staff because a coach "is a significant other" to a student.

   1983 June 21, William E. Geist, “High Schools Struggle with Coach Shortage”, in New York Times, retrieved 27 Oct 2013

   2 more examples

   As in the rest of the hospital, a family member or "significant other" such as a lover or close friend, is allowed to spend the night in a patient's room on a cot.

   1985 December 14, Katherine Bishop, “Ward 5B: A Model of Care for AIDS”, in New York Times, retrieved 27 Oct 2013

   If your spouse, children or other significant others are still whining about all those holiday leftovers you made them eat, maybe it's time to spruce up your culinary skills.

   1989 December 26, Graham Vink, “Not At Home On The Range”, in Spokesman-Review, retrieved 27 Oct 2013, page F1