I asked this question a while ago, and I still disagree with it being closed as off-topic. The reason given for closing the question is that commonly-available references can answer it. I mentioned in the question that the commonly-available references all point to the legal definition. I think it should be reopened. If not, can you help me understand why it should remain closed?
I consulted some synonym dictionaries, and I can confirm Nathan L's research results: most dictionaries focus on the failure/forfeit sense of default. In fact, default in the sense of "automatically selected preference" (which originated as a computer-related term but has subsequently gained traction in more-general use) first appeared in the Merriam-Webster's Collegiate Dictionary series in the tenth edition (1993), which indicates relatively recent mainstream adoption of the usage.
The closest adjectives to default in the relevant sense that I can think of are go-to and fallback, and neither of those is an especially good match for it.
It would be interesting to know how the computer meaning arose. My guess is that it originated in the sports metaphor of advancing to the next round in a bracketed tournament because the listed opponent forfeited the match. I can imagine a computer programmer treating a user's declining to alter the program's baseline settings as a kind of forfeiture of the opportunity to customize the settings, for example.
But this is quite aside from the legitimacy Nathan L's question about what words might serve as synonyms for default in its new sense. As far as I can see, it isn't a general-reference question. I therefore support his request to reopen the original question.
Currently, three of the four reasons given by close-voters seeking to reclose the original question cite its lack of an example providing context. To repeat a comment I made beneath Nathan L's original question, he seems to be asking about a situation in which, for example, default is used as a noun, as in "The 'Sell my personal data to anyone on the Internet who wants to buy it' option is the default." But a similar question could be asked about the use of default as an adjective, as in "Clicking 'Revert' causes the program to revert to its default settings."
It should go without saying that if you can show that commonly available references do not provide the information that you need, your question should not be closed, and if it is closed, you have every right to ask for it to be re-opened.
However, in your particular case, it is hard to see what good it would do. If there were a good single-word synonym for default value, it would be listed in thesauri and other reference works, and software developers would already be using it. Also, the fact that you have already accepted an answer does nothing to help your case.