Mastro Posted in M Best definition Mastro A Person who has a penis shaped head. Look at that kid, he has a mastro Mastro: define #2 Mastro Adj. Acting like a spoiled rich brat. AJ is so mastro showing off his new car. How satisfied are you with the definition? Looking for Mastro meaning? Delighted that you discovered the greatest determine on our web site! Recently this definition was actually observed 74 times.