When I'm reading an article and come across a word I don't know, in many applications I can simply click the word for a definition. Either the definition comes right up or I get a sub-menu that allows me to click "look-up".

I downloaded the dictionary add-on but I think it's a library for when you're typing. I want something I can look up while reading. I'm having a hard time getting to that so I'm here to ask for help. Thank you in advance.