Where "Defo" Comes From
"Defo" applies the "-o" suffix to "definit-" (clipped from "definitely"), creating a two-syllable shortening that is faster to say and type than the full word. It follows the same word-formation model as "arvo," "servo," and "smoko" — the "-o" suffix being one of the most productive patterns in Australian informal English.
While Australian in character, "defo" spread into British informal English and international text-messaging culture from the early 2000s, when SMS character limits made abbreviation genuinely useful. It signals casual directness — "defo" means definitely, with no hedging.
Source:
"Defo coming to the barbie."
How Aussies Actually Use It
Used as an enthusiastic, casual confirmation — "defo coming to the barbie" carries the same certainty as "definitely" but with a lot more informality.
It's especially common in texting and among younger speakers, though it's crossed into general spoken slang too.
🎓 Want to sound like a true Aussie?
Watch Down Under English on YouTube for real Australian pronunciation, slang lessons, and culture — taught by an Australian educator.
Watch on YouTube →