Conjoined Account
You've heard of conjoined twins, right?
Siblings who didn't quite separate in the womb and now share a liver and most of their intestines and, barring medical intervention, will have to spend every waking moment together forever.
Think double toilets. And double honeymoons.
Well, a conjoined account is kind of like that. It's a financial account that has more than one owner. The people are financially stuck together in the account. All the people included in the conjoined account have equal access to it.
The most common example in real life is a joint checking account for a married couple. Either person can write checks off the account or take out money. It all works out, until one day, you wake up to find the account empty, the car missing, and a note on the counter that just says “It's been fun, but I'd rather be in Santa Fe.”