Dictionary App constantly downloading dictionaries

Solution 1:

This kept happening to me too, again with the recent update to 10.13.4. In dictionary preferences, I had selected multiple dictionaries. Turning them off, restarting the app, and turning them back on resolved the issue.

Solution 2:

I've experienced this problem once in a while, and find that it's due to the DictionaryServiceHelper process freezing. To fix it, first I quit Dictionary, and then I open a terminal and type:

pkill -9 DictionaryServiceHelper

Yes, you really do need to send the dangerous SIGKILL (signal 9) in this case.

If you're not a command line person, you can alternatively open Activity Monitor, search for DictionaryServiceHelper, and force quit it.