Two Fantastic Chrome Extensions for students and teachers:
View definitions easily as you browse the web.With this extension, you can:
1) Double-click any word to view its definition in a small pop-up bubble.
2) View the complete definition of any word or phrase using the toolbar dictionary.
Google Image Dictionary (install Chrome Extension)Quickly look up an image of the highlighted words without leaving your current page. Looks up the highlighted words and displays the closest matching image in a popup bubble.(The only drawback on this one is that it uses wikipedia.org for images so consider the source and always double check validity.)
Use it 2 ways:
1) Hold Alt double-click any word.
2) Highlight some text, right-click, click Image Search. Click again to remove the image.