When you lose a lot of money doing something dumb or doing something with virtually no knowledge of why you are doing it. Named after the soon to be ex-hedge fund manager Whitney Tilson and made famous by the blog Zerohedge
you see a guy winning at craps so you follow all his bets and then he craps out and you lose all your money -- "Man I just got Tilsoned
on the craps table"
or in the world of finance when a hedge fund or investor loses a lot of money copying someone else's idea: man I just got Tilsoned
again and lost the whole position.