If it passes with 2/3rds senate approval and the president does not sign it, it becomes law in ten days

The one catch is that congress has to be sitting at the ten day mark, if not the bill dies.

Several sites confirmed this on a search for 'what happens if the president does not sign.....' it auto fills the rest, the question had been asked so frequently 

A 2/3rds passed bill cannot be vetoed.., only not signed...