It’s a common dictionary, which is probably not very good in this context. I think it would be more appropriate to refer to ISTQB, as it is likely the most relevant source when it comes to software testing and failures:

Human beings make errors (mistakes), which produce defects (faults, bugs), which in turn may result in failures. Humans make errors for various reasons, such as time pressure, complexity of work products, processes, infrastructure or interactions, or simply because they are tired or lack adequate training

Or to put it simple:

We’re seeing a failure here.

Pellaeon started as Rukh brushed silently past him; he hadn’t realized the Noghri had followed them down. Thrawn waited until Rukh was standing at his side, then turned back to Colclazure. “Do you know the difference between an error and a mistake, Ensign?”

The entire bridge had gone deathly still. Colclazure swallowed again, his face starting to go pale. “No, sir.”

“Anyone can make an error, Ensign. But that error doesn’t become a mistake until you refuse to correct it.” He raised a finger-

And, almost lazily, pointed.

Pellaeon never even saw Rukh move. Pieterson certainly never had time to scream.

- Hier to the Empire, by Timothy Zahn