GoldenDict is a very useful dictionary look program, I have yet to find something similar in Linux with all the features that GoldenDict provides.
You can install it Mint by.
sudo apt-get install goldendict goldendict-wordnet
Noticeably ,the very useful of its features is Scan Popup. In fact, I accidentally found this app by searching for this functionality. What it does is it pop-ups with the word meaning when you select a word. This can be a little more customised, like you can specify it to only open when selected keys are pressed. By default Scan Popup functionality is disabled in GoldenDict. You can change it in preferences and make it always start with Scan Popup turned on.
There are many other features in it which you can enable from the preferences. Don’t forget to install goldendict-wordnet package it will aid as offline dictionary which I found very useful. Ofcourse you can install many other supported dictionaries, by default it comes with Wikipedia enabled. You might find it very useful.