built-in Dictionary popup font size

Not for the popup. You can go into the Dictionary preference though and change the contextual menu to change from popups to actually opening the word in the dictionary.

 

Yes, there is

yes, there is a way. I forgot how I accomplished this on my MBP before upgrading to a newer model and found this thread. I'll post the steps when I can.

You need to edit the CSS file located here:

`/Library/Dictionaries/Oxford Dictionary of English.dictionary/Contents/DefaultStyle.css`

Open in a text editor and, depending on your last update/version of os, head down to line 970. Look for this selector:

`html.apple_client-panel body`

It should have a default value of 14px (lower value of px means smaller font and vice versa). You will need to restart after you save (browser).