What does the Latin 'Pont Max' stand for?

The Latin phrase 'Pont Max' stands for Pontifex Maximus, which means 'high priest' or 'chief priest'. In the word-by-word translation, the noun 'pontifex' means 'bridge-builder'. It's formed from the combination of 'pons', as 'bridge'; and 'facio', as 'I make, I build'. The adjective 'maximus' means 'greatest'.

Note: May I add, just in case the asker wasn't aware, that 'Pont Max', or, as stated before, 'Pontifex Maximus', is generally used in reference to Popes of the Catholic Church. Monuments will often carry inscriptions such as "Gregorivs XVI Pont Max Anno XIV", in reference to a specific Pope (in this example, Gregory XVI). The term used to be used in reference to bishops in general, but became a common title for the office of the Pope.