QuickDef

QuickDef is a Chrome extension that delivers AI‑generated word definitions directly on the page being read. By double‑clicking any term on a website or within a PDF, a popup shows a concise explanation, allowing users to stay in the reading flow without opening new tabs or copying text.

The service targets English language learners, offering “learner‑first” explanations written in plain English at an A2–B1 CEFR level and based on the surrounding sentence. A traditional dictionary mode is also available, providing phonetics and audio pronunciation for users who need more detailed lexical information.

In addition to instant definitions, QuickDef lets users save words with their context for later review, supporting a simple flashcard‑style study workflow. The extension works on web pages and PDF documents, addressing the gap left by other dictionary tools that do not function within PDFs.