POSSLQ

[ pos-uh l-kyoo ]
/ ˈpɒs əlˌkyu /

noun, plural POSSLQs, POSSLQ's.

either of two persons, one of each sex, who share living quarters but are not related by blood, marriage, or adoption: a categorization used by the U.S. Census Bureau.

Origin of POSSLQ

p(erson of the) o(pposite) s(ex) s(haring) l(iving) q(uarters)