The "reverse dictionary" is called a "thesaurus". Wikipedia quotes Peter Mark Roget (1852):
> ...to find the word, or words, by which [an] idea may be most fitly and aptly expressed
Digital reverse dictionaries / thesauri like https://www.onelook.com/thesaurus/ can take natural language input, and afaict are strictly better at this task than LLMs. (I didn't know these tools existed when I wrote the rest of this comment.)
I briefly investigated LLMs for this purpose, back when I didn't know how to use a thesaurus; but I find thesauruses a lot more useful. (Actually, I'm usually too lazy to crack out a proper thesaurus, so I spend 5 seconds poking around Wiktionary first: that's usually Good Enough™ to find me an answer, when I find an answer I can trust it, and I get the answer faster than waiting for an LLM to finish generating a response.)
There's definitely room to improve upon the traditional "big book of synonyms with double-indirect pointers" thesaurus, but LLMs are an extremely crude solution that I don't think actually is an improvement.
> Best match is versatile which usually means: Capable of many different uses
with "multi-purpose", "adaptable", "flexible" and "multi-use" as the runner-up candidates.
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Like you, I had no idea that tools like OneLook Thesaurus existed (despite how easy it would be to make one), so here's my attempt to look this up manually.
"Admitting a large number of uses" -> manually abbreviated to "very useful" -> https://en.wiktionary.org/wiki/useful -> dead end. Give up, use a thesaurus.
Taking advantage of the fact my passive vocabulary is greater than my active vocabulary: no, no, yes. (I've spuriously rejected "multipurpose" – a decent synonym of "versatile [tool]" – but that doesn't matter.) I'm pretty sure WordHippo is machine-generated from some corpus, and a lot of these words don't mean "very useful", but they're good at playing the SEO game, and I'm lazy. Once we have versatile, we can put that into an actual thesaurus: https://dictionary.cambridge.org/thesaurus/versatile. But none of those really have the same sense as "versatile" in the context I'm thinking of (except perhaps "adaptable"), so if I were writing something, I'd go with "versatile".
Total time taken: 15 seconds. And I'm confident that the answer is correct.
By the way, I'm not finding "multifarious" anywhere. It's not a word I'm familiar with, but that doesn't actually seem to be a proper synonym (according to Wiktionary, at least: https://en.wiktionary.org/wiki/Thesaurus:heterogeneous). There are certainly contexts where you could use this word in place of "versatile" (e.g. "versatile skill-set" → "multifarious skill-set"), but I criticise WordHippo for far less dubious synonym suggestions.
'multifarious uses' -> the implication would be having not just many but also a wide diversity of uses
M-W gives an example use of "Today’s Thermomix has become a beast of multifarious functionality. — Matthew Korfhage, Wired News, 21 Nov. 2025 "
wordhippo strikes me as having gone beyond the traditional paper thesaurus, but I can accept that things change and that we can make a much larger thesaurus than we did when we had to collect and print. thesaurus.com does not offer these results, though, as a reflection of a more traditional one, nor does the m-w thesaurus.
So you weren't actually using the thesaurus as a reverse dictionary here. The thesaurus contains definitions, and the reverse dictionary was the search tool built into their website. It would work just as well against a dictionary as a thesaurus.
Importantly to the point being discussed, what you did does not work at all against an actual physical thesaurus book.
If the thesaurus had an entry for "very useful" (as WordHippo does), then yes, it would work against an actual physical thesaurus book. This whole cluster of words is coded into Wiktionary incorrectly – for example, https://en.wiktionary.org/wiki/utility#Synonyms is a subsection of "Adjective" despite listing synonyms for a sense of the noun:
> (state of being useful): usefulness, value, advantages, benefit, return, merits, virtue, note
where "note" is a synonym of distinction, not utility, and Thesaurus:utility has fewer entries than this. Versatility should be listed in Thesaurus:utility as a related concept.
Paper thesauruses (thesaurai?) won't have prefixes like "very" in their pages.
Furthermore, even if we allow "very useful", that's a far cry from "admitting a large number of uses". The latter requires a search engine to properly map.
Which they've been good at for a while. You could have googled "word meaning admitting a large number of uses" back in 2018 and gotten good answers.
My point is, the tools you've linked to are useful/versatile, but it's not the thesaurus that makes them so useful, it's the digital query engine built on top of the thesaurus.
Even if I don't know the word "versatile", I can go from the phrase "admitting a large number of uses" to the phrase "very useful". The original point I made (before I discovered OneLook Thesaurus) described the effectiveness of a procedure that was just manually looking things up in databases, as one might do in a paper thesaurus. (I could print out Wiktionary and WordHippo in alphabetical order, buy a Cambridge Thesaurus and some bookshelves, and perform the procedure entirely offline, with only a constant factor slowdown.)
They've got that information scattered around a few pages. The Help page says they use (a modified version of) Datamuse for lookup, with Wikipedia, Wiktionary and WordNet providing dictionary definitions. The Datamuse API (https://datamuse.com/api/) uses a variety of GOFAI databases, plus word2vec: it's all pre-2017 tech. OneLook additionally uses https://arxiv.org/abs/1902.02783 for one of its filters (added 2022): more details can be found on the Datamuse blog: https://www.datamuse.com/blog/. https://web.archive.org/web/20160507022201/http://www.oneloo... confirms the "longer queries" support (which you described as "LLM-like") was added in 2016, so it can't possibly be using LLMs; though I'm not sure how it does work. There may be some hints in the OneLook newsletter (e.g. https://onelook.com/newsletter/issue-10/ (10 July 2025?) cryptically notes that "Microdefinitions are algorithmically generated […] they go through a series of automated cross-checks against public domain dictionaries, and the suspicious ones are vetted by humans"), but the newsletter isn't about that, so I doubt there's much information there.
> ...to find the word, or words, by which [an] idea may be most fitly and aptly expressed
Digital reverse dictionaries / thesauri like https://www.onelook.com/thesaurus/ can take natural language input, and afaict are strictly better at this task than LLMs. (I didn't know these tools existed when I wrote the rest of this comment.)
I briefly investigated LLMs for this purpose, back when I didn't know how to use a thesaurus; but I find thesauruses a lot more useful. (Actually, I'm usually too lazy to crack out a proper thesaurus, so I spend 5 seconds poking around Wiktionary first: that's usually Good Enough™ to find me an answer, when I find an answer I can trust it, and I get the answer faster than waiting for an LLM to finish generating a response.)
There's definitely room to improve upon the traditional "big book of synonyms with double-indirect pointers" thesaurus, but LLMs are an extremely crude solution that I don't think actually is an improvement.