How to remove Merriam Webster from my browser and to add Oxford Dictionary?

Question

Hello,
When browsing for definitions and synonyms, it is always Merriam Webster that comes up, first and over again.
I would much rather prefer using proper Oxford English Dictionary, or at least Cambridge (the one in Mass, not necessarily the original in UK).
How and where can I find an option to disable Merriam Webster and add Oxford as my primary dictionary?
My language is set to English (UK), but it doesn't help.

Regards
AZMB