Folks often ask for a definition of IT project failure. This video from the Strategy Lab blog offers a somewhat simplistic, but still accurate, explanation.
I'm paraphrasing, but the video says that projects are considered a failure when they are over-budget, late, or do not deliver expected planned results. Perhaps most importantly, it correctly points out how differences in measures of success between customers and vendors influence perception of failure.
The video is only a few minutes long and worth a view.