Looks up online Shabdkosh Dictionaries (includes English and 10 Indian languages) for the selected text.
Just right-click on the selected text and choose "Shabdkosh Dictionary...". Before that, you can choose a Indian language that you want on the Shabdkosh Dictionary popup (click on the extension's icon to show the popup. You should pin the icon right after installing the extension). And you can also look up there.