How can I turn off Google's pop up when I click on words?

Alex here, designer of Langua. Whilst listening to content on Langua, I was finding it annoying that when I clicked on a word, a translation would pop up from Google at the bottom of the screen. Whereas I only wanted to see Langua's translation box, which is typically more accurate and provides examples.

I thought it was Google Translate, so I turned that off. No luck.

After a lot of searching, I finally found the culprit: 'touch to search'. The below 1-minute YouTube video explains how to turn it off, in case you want to do the same.