2. The phrase is more commonly misused to describe a movie of noticably poor quality.
3. It is rarely used to describe a movie with a low profit margin regardless of budget size, but I have heard it used this way occasionally.
2. "That might have been the worst movie I have ever seen. I wish the reviewer had mentioned it was a b movie"
More often than not these films can be enjoyed with a group of friends armed with large quantities of alcohol and be found more entertaining than anything with enough budget to make blood not look like strawberry toothpaste.
Can also be connected to an 'A-movie' with a cult following or all the qualities listed above.
Anything directed by Alex Chandon is a B movie (or soft porn).
Alien resurrection has more plot holes than Stars Wars episode III and is more unnecessary than episodes I, II and III - and therefore should be a B movie.