1.  Select text or tap on existing highlight, underline or cross out annotation that you wish to define or translate. 

2. Tap the Define or Translate button in the quick menu that appears.

Note: You may have to press the overflow (three dots) button to access the Define or Translate buttons. 

3. A popup appears with the definition or translation.

Note: For translations, you can tap on the source or target language to change it.