Fastest way to search on Google or find meaning of word

First is to activate a feature called "Copy Aide" from settings. As the name suggests, you just have to select some text and hit the copy button to see the definition of the word.
It can be easily paused from the notification when not needed.
Enabling the + button shows you a pop-up with the copied text, which is useful in apps like WhatsApp where a word can't be selected singularly from the chats

- Second is to Share the text and click on Define

- Third is to use the homescreen widget.

- For Play Books you can also use "Web search" feature. And for Moon+, FB Reader dictionary feature, choose "ColorDict"

Offline definitions available in 5 languages: English, French, German, Italian and Spanish (A very big thanks to Livio for providing access to their data)
To get more languages, you can also use my app Dict Aide, which supports StarDict dictionary packs.