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.