Definition
A euphemistic way of saying that one needs to leave, often to go to the restroom.
"I've got to see a man about a dog; I'll be right back," he said as he hurried to his feet.
When asked where he was going, he simply said, "I've got to see a man about a dog."
"I'll be back in a jiffy," she said, using 'see a man about a dog' as a convenient excuse to leave the room.