Nisus Thesaurus

Nisus Thesaurus is an electronic reference that provides synonyms and related terms for any word selected in a macOS application that supports the Services menu. After highlighting a word, the user invokes Nisus Thesaurus from the Services list, and the synonym list appears in a separate browser window, allowing quick navigation through related entries. The database is built on WordNet and contains more than 120 000 English words, organized into six relational categories.

The tool is designed for macOS users who need a lightweight, ad‑free thesaurus that works across a range of applications such as Safari, Apple Mail, TextEdit, and the Nisus Writer suite. Integration is achieved through the standard Services framework, so no additional plug‑ins or extensions are required. A built‑in glossary provides definitions alongside synonyms, enhancing the lookup experience.

Nisus Thesaurus is distributed free of charge, with no advertising or tracking, and is maintained as a stable product for macOS. It targets writers, editors, and anyone who frequently consults synonyms while working in any services‑aware Mac application.