QuickDef – AI Dictionary for PDFs & English Learners

Look up any word — or a whole phrase like "put up with" — with AI definitions built for English learners. Works in PDFs too.

NEW IN 1.2.0 — PHRASE LOOKUP Dictionaries can only look up one word at a time. That's why "put up with" never works: you get definitions of "put", "up", and "with", and none of them mean "tolerate". Now you can drag across the whole phrase and click Define. QuickDef explains what the expression means together — phrasal verbs, idioms, fixed expressions — in plain English, based on the sentence you're actually reading. * put up with → to accept something unpleasant without complaining * bear in mind → to remember something important when you decide * a piece of cake → something very easy Double-click still works exactly as before for single words. ——————————————————————————— Look up any word — or any phrase — without leaving the page you're reading. Double-click a word, or drag across a phrase — 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. PHRASES, NOT JUST WORDS A dictionary indexes one word at a time, so "put up with", "bear in mind" and "a piece of cake" have no entry to find — the meaning isn't in any of the individual words. Select the phrase, click Define, and QuickDef explains the expression as a whole. Phrasal verbs and idioms are how English is actually spoken, and they're the part learners get stuck on. 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, works on words and phrases • Dictionary — full entry with all parts of speech, phonetics, and audio pronunciation Switch between them in one click. BUILD YOUR VOCABULARY Save any word or phrase together with the sentence it appeared in, not just the word alone. Review saved items 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 — words and phrases both • 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 — especially anyone who knows the words in a sentence and still doesn't know what it means. 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).