An exceptionally lucky person.
 I'd be happy to be a tin arse for just one day at the races
 Example sentencesExamples
-  Never praise a good shot – 'Tin-arse!' is the highest praise allowed.
 -  Luke couldn't believe my tin arse since I had picked the winner 'again' when we were betting together.
 -  Bob came out of it all right, didn' yer Bob? Tin arse Bob they call 'im.
 -  His reputation as a tin arse lasted right to the end of his stay in the States.
 -  Have been a total tin arse in the last year, Dad must be sending me luck!