Fluke
British SlangDefinition
An unexpected stroke of luck; an accidental success achieved by chance rather than skill (also used as a verb: to achieve something by luck).
Examples
"He only passed his driving test by a fluke after the examiner got distracted."
"I fluked the winning shot in extra time; nine times out of ten I’d have missed."
"What a fluke, the last train was cancelled, so we got a refund and a lift home."