Free Arabic-Arabic and Arabic-English dictionary aggregating the classical lexicons.
Details
The lookup most Arabic speakers and advanced learners actually use: it pulls together Lisan al-Arab and other classical dictionaries alongside modern bilingual entries, with roots, conjugations and idioms. Monolingual definitions make it the natural step up when English glosses stop being precise enough. The site is ad-heavy, the interface is cluttered, and it covers formal Arabic only — dialect words will not be there.