1. dated slang A piano. Sometimes hyphenated or spelled as a single word. He found his way to the joy box in the corner and started playing classic Christmas tunes. She's one of the best musicians to ever grace a joy-box.
2. vulgar slang The vagina. I told him that he wasn't going near my joy box until after we were married.
n. a piano. (see also tinklebox.) Can you play this joybox at all?