Defo

[TigerJillMoran]

"Defo". Can these lazy bastards people not spell definitely? It's everywhere!

Definitely is a challenge! I often seem to email people to inform them that I'm going to our next meeting defiantly.

I've seen 'definately', too. I wonder what these autocorrects do?

Autocorrect seems to render it as 'defiantly', which used to be mildly amusing ('I will defiantly see you for lunch on Tuesday!'/ 'He is defiantly wrong!') until I realised that people who seldom read newspapers or books, and who encounter most of their writing in online chatroom/social media settings, think that this is actually how 'definitely' is spelled. See also 'ect', 'walla', the notorious 'Chester draws' and quite a few others.

It's not so much that it's an individual person's error, it's that if people see it often enough in their only contact with the written word, it hardens into a widespread delusion.

Defo has been in use as a short form of definite or definitely for decades.
DEFO definition and meaning | Collins English Dictionary