Who uses it: Members of the Church of Jesus Christ of Latter-day Saints (Mormons)
What it means: Taking more than one wife, which the rest of us call bigamy or polygamy.
How you can use it: You shouldn't, and I'll explain why.
The Mormon Church rejected the doctrine of plural marriage years ago, but the fact that they still refer to it by this term -- rather than as polygamy -- shows me, and the world, that they haven't recoiled from the idea entirely. Words are powerful. Polygamy is a crime and something practiced by cultures we consider primitive; plural marriage sounds reasonable and even kind of cozy.
I'm torn about whether to watch the HBO series "Big Love." It looks very entertaining, and I'm a big fan of Bill Paxton (A Simple Plan is one of my favorite movies, and Frailty is one of the scariest films I've ever seen). But polygamy is not benign or funny, even where it's (theoretically) voluntary.
Today is my parents' 41st wedding anniversary, so I wish Dad happy anniversary -- because it will always be their anniversary, as long as anyone is around to remember it.