Man, that brings back memories.

I just found the following via Mr Google, but knowing nothing about the purveyor I'm a tad wary of accessing it:

Oxford English Dictionary (free version) download for Mac OS X
https://en.freedownloadmanager.org/Mac-OS/Oxford-English-Dictionary.html

Feb 1, 2016 - Free download Oxford English Dictionary forMacOSX. Oxford English Dictionary - The foremost single-volume authority on the English language - revised and updated in 2010 to include the very latest vocabulary.