What does defo mean?
'Defo' is an informal British adverb meaning 'definitely' or 'certainly', used to express firm agreement or emphasis in casual conversation. It arose as a spoken and written abbreviation of 'definitely', clipped in typical English fashion to its opening syllables with an '-o' ending, a pattern seen in other colloquialisms such as 'arvo' (afternoon) in Australian English. Commonly heard among younger speakers and widespread in text messages and social media, it appears in exchanges like 'Coming Saturday?' — 'Defo.' The word carries a breezy, friendly register and can signal enthusiasm as much as certainty. It occasionally appears in the alternative spelling 'deffo'. Because it belongs firmly to informal speech, it should be avoided in formal writing, but in relaxed contexts it offers a quick, punchy way to say yes with conviction.
adverbAn informal British abbreviation of 'definitely', meaning certainly or without doubt.
- Certainly; definitely (informal British slang, an abbreviated form of 'definitely').
"Are you coming to the pub tonight? Defo."
"Fancy a curry later? Defo."
"She's defo the best person for the job."
One word, two syllables saved: 'defo' is what happens when Britons decide 'definitely' is just too much effort.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of defo
'Defo' is a modern colloquial clipping of 'definitely', itself derived from 'definite', which comes from Latin 'definitus', the past participle of 'definire' ('to set bounds, define'), from 'finis' meaning 'end' or 'boundary'. It emerged in late twentieth-century British informal speech, particularly among younger speakers, following the familiar English habit of abbreviating long words and adding '-o'. It shares its ultimate root with words such as 'definition', 'definitive', and 'finite'.
How defo is actually used
Strictly informal and conversational, common in texting and casual speech in Britain and Ireland; avoid in formal or professional writing. Spelled sometimes as 'deffo'.
Easily confused with defo
'Deco' refers to the Art Deco design style, whereas 'defo' is informal slang for 'definitely'.