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)
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
1979, acronym from person of opposite sex sharing living quarters; it never was an official category.
Online Etymology Dictionary, © 2010 Douglas Harper