In general answers in any subnet of SE should follow some specific guidelines. These should also be a must read (or even better a forced read) for every user.
I personally for example didnt even read them at all (neither did I bother to even look them up).
To answer the initial question: There is nothing inherently wrong with one line answers (as long as they are not unarguably wrong content-wise) (for example the programming sites of SE have masses of oneliners just because there are often questions being asked that are simple / trivial enough to be easily answered in one sentence or line (of code). Although providing atleast one full (ever so short but full) sentence as an answer should be minimum-requirement. Especially for single word request questions this is in my opinion acceptable as long as the word in the oneliner is most definitely acceptable to be common knowledge. In contrast more unusual, old, very creative or outright obscure answers should be as always be very well explained / documented.
As a summary and food for thought think about the following somewhat related question: What is the minimum acceptable length for a Ph.D thesis?
One answer one of my professors gave me on that was the following story:
The shortest thesis he's aware of comes in at ONE (1) A4 page! How is that possible? The thesis was written by a mathematican and was a proof for some really old and (in the math-scene) well known (until then) unprooven theorem... And that proof took the math guy in fact all the time of study on the subject. Then the mathematic-notation, in a short and concise manner maybe even using specially just for the purpose defined symbols do the rest in shrinking everything down. And as long as it was either self explainatory from an algorithmic point of view or as long as the math guy could explain it during the approval session everything is fine.