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.