The question you pose is undecidable.
Dictionaries are DEscriptive, not PREscriptive. They record how legions of fallible humans collectively usually use words. They aren’t some linguistic government which commands exactly how we all must always use the language.
English (or any natural human language) is simply a collection of more-or-less agreed-upon conventions.
We collectively agree that the symbol “cat” refers to whatever we agree it refers to. And we don’t have 100% agreement.
There is no central authority. Repeat after me, there is no central authority. As such, there is no perfectly unambiguous and non-conflicting definition of anything.
I call it the Linguistic Uncertainty Principle (with apologies to Heisenberg).
Definitions only get so precise. Putting a word’s definition under a magnifying glass reveals a fuzzy edge, not a sharp edge. And more magnification simply reveals more fuzziness, not a sharper view of the fuzziness. The closer you look, the more elusive the edge becomes.
It’s like Heisenberg’s quantum mechanical Uncertainty Principle in that greater precision simply does not exist and cannot be created by any tool or method. Obviously it’s unlike quantum mechanics in that the state of the definition doesn’t change in response to observation. (Although your understanding of it may.)
It follows therefore that the meaning of sentences cannot possibly be more precise than the meaning of the words they contain. So the longer the sentence, the more ambiguous it must be. Much like tolerances add up in engineering. Yes, you can try to offset some of that with clever sentence structure, but that only goes so far.
Once you get to paragraphs and books, the situation is out of control, at least in an engineering sense.
For example, if you and I were to read a particular novel, ideally exactly the same thought pattern would form in our respective heads. After all, the author only had one idea pattern, so why should we have differing ones?
But the underlying imprecision of the tools used to transmit that idea, namely language, limit the fidelity of your and my attempts to reproduce the author’s thinking.
Now certainly governments can and do pass laws which contain carefully chosen definitions of certain terms, such as “civilian”.
BUT, continuing with that word as an example, there is no legal, moral or logical requirement that the US Dept of Defense use the same definition as the NJ state laws, much less those of other states or counties or cities or other countries or prefectures or provinces or …
The “official” definition depends entirely on who or what you choose to take as your source. Context will make some sources clearly less relevant that others, but it’s doubtful that any one source will be universally “better” for any single question, much less for all questions.