Google introduced Now on Tap feature with Android M and has carried it on with Android N. As the feature has matured over a period of time, it has added functionalities too. So far, Now on Tap was restricted to only recognizing fragments of text on the display of which you had little control. It was mainly stuff like looking up a restaurant contact details and things like that, which were supported. However, with the latest update that has just started rolling out, you will be able to do more, which includes looking up word definitions and reverse lookup images for relevant information. Before we get to how to do it, make sure you have your Google Search app updated to the most recent update.
In order to search for a word definition, all you need to do is select the word and you will see an underlying box with the definition of the word as well as the Google Search of the word right there. Alternatively, what you can do is select the word or set of words and then simply long press the Home button to call Now on Tap in action.
The moment it reads your screen, you will be given the definition of the word as well as the option to look the word up on Google’s services based on the content relevancy. You can also reverse lookup the images now using Now on Tap.
All you need to do is to have an image on your screen and long press the Home button to call a reverse lookup. This words literally anywhere on Android and all you need to do is to have the image and call the feature. Unfortunately, this is available only on Android Marshmallow and Android N, though it definitely looks like a cool feature that older Android versions could do with.