Context would be helpful. This can indicate a blockage of some kind. For example, if you flush a towel down the toilet then the pipe (or plumbing) will be backed up with the towel. It is also common to use this to indicate that you cannot do something because you are busy. You are blocked from doing something by something else. For example, "I cannot go see the movie because I am backed up with work." In this case, you are busy with work, which is blocking you (in a way) from seeing the movie.

how was it used?