I was a fan of the package Dictionaries but is seems that it is no available and that will not be re-included. The package’s page in package control is here, indicating that the package was removed.

Anyway, the package is in GitHub and it can be installed from the repository. The steps follows:

• Download the package as a ZIP file
• Open a terminal on your Downloads folder
• Unzip the file with unzip Dictionaries-master.zip
• Rename the folder in a more suitable name with mv Dictionaries-master Dictionaries
• Move the unzipped content to you package-folder with mv Dictionaries ~/.config/sublime-text-3/Packages

The steps described here are also in the package’s repository (at the end).