"No definition found"
An Apple Support discussion, iPhone 5, my 'define' word feature no longer is an option. How can I get it back?, suggests the following:


  
  Go to Settings > General > International > Language
  Change the language to one of Apples supported languages like Spanish.
  Go to your notepad, type "test", press hold, select the word, and click the "define" that now appears.
  This will tell you there is no current dictionary, and prompt for one to be downloaded.
  Assure you are on a stable Wi-Fi network, and hit download.
  Once complete, go back to your language settings and switch back to your native language.
  Enjoy your dictionary feature without having to "reset" your phone.