Definition from Wiktionary, the free dictionary
Alternative forms 
- (UK, originally Ireland, slang) To ruin or destroy.
- For more quotes, see the citations page
- 1928, Eimar O'Duffy, The Spacious Adventures of the Man in the Street, Macmillan, p. 370,
- Indeed, it seemed that the army was hopelessly banjaxed.
- 1970 (2001 reprint), Edna O'Brien, A Pagan Place, Houghton Mifflin Harcourt, p. 91,
- Emma had suggested that you hide, said your presence might banjax her position.
- 2006, Craig Ferguson, Between the Bridge and the River, Chronicle Books, p. 252,
- Fraser was looking at the flat, wet countryside and thinking about the French policeman who had banjaxed him with the truncheon.
To ruin or destroy
banjax (plural banjaxes)