QuickDef – AI Dictionary for PDFs & English Learners

AI dictionary for English learners that works on PDFs and web pages. Double-click words for simple meanings.

Look up any word without leaving the page you're reading. Double-click a word — on any web page or inside a PDF — and QuickDef shows you what it means, right there. No new tab. No copy-paste. No losing your place. WORKS ON PDFs Most dictionary extensions silently fail inside Chrome's PDF viewer. QuickDef was built for it. If you read research papers, textbooks, or reports as PDFs, this is the difference. DEFINITIONS THAT MATCH THE SENTENCE Traditional dictionaries list every possible meaning and leave you to pick. QuickDef reads the sentence the word appeared in and explains the meaning it has *there*. Look up "bank" in a finance article and you get the finance meaning. WRITTEN IN PLAIN ENGLISH Dictionary entries are written for fluent readers and often define a word using vocabulary harder than the word itself. QuickDef's AI mode targets CEFR A2–B1 — the explanation stays simpler than the term. TWO MODES • Explain — plain-language AI definition, context-aware • Dictionary — full traditional entry with all parts of speech, phonetics, and audio pronunciation Switch between them in one click. BUILD YOUR VOCABULARY Save any word together with the sentence it appeared in, not just the word alone. Review saved words later as flashcards. Everything syncs to your account across devices. START WITHOUT AN ACCOUNT No signup, no email, no credit card. Your first double-click just works. FREE PLAN • 10 AI definitions per day • 25 saved words • Unlimited traditional dictionary lookups — always PREMIUM — $3.99/month or $29.99/year (about $2.50/month) • Unlimited AI definitions • Unlimited saved words • Email support Cancel anytime. WHO IT'S FOR English language learners reading in English. Students working through academic papers. Professionals reading reports and documentation in a second language. Anyone who reads enough to be tired of opening a new tab for every unfamiliar word. Works in Chrome and Chromium-based browsers (Brave, Edge, Opera, Arc).