Is the ceiling actually the floor

Some guy who was walking on the ceiling today told me that he was actually walking on the floor. Is this true? Is the ceiling actually the floor?

Floor: The lower surface of a room, on which one may walk

If you can walk on the ceiling, then it can be the floor. Since there would be no gravity if you're walking on the ceiling, then there would be no ceiling or floor, you're just walking on the walls.