A type of photographic camera (usually of the view camera type), but not necessarily) where the body of the camera is a soft, flexible bellows. A bellows camera is made more or less like this:
| = lens fixed in
| film = front plate
------------------------- focusing rail or focusing bed
the /\/\/ is the bellows. As you can see from the disgusting ASCII diagram, the front plate and the back plate are mounted on a rail or bed that allows them to move back and forth for focussing.
Most bellows cameras are large format cameras, although there are some bellows cameras that use 120 film.
bellows camera is also defined by Webster 1913 under bellows, but he didn't provide an ASCII art diagram, chiefly because he didn't have ASCII, and perhaps if he had known he would have despised ASCII art