1. to ruin, spoil, or wreck something; to break or damage
Usage: informal; chiefly Irish and British English
2. to thwart or foil a plan or attempt
Usage: informal; chiefly Irish and British English

Examples

• The storm banjaxed our outdoor wedding plans.
• He banjaxed the car engine by driving it without oil.
• Don't banjax this opportunity by being late.
• The injury banjaxed his chances of playing in the final match.
• She accidentally banjaxed the computer when she spilled coffee on it.
• The scandal banjaxed his political career.