Donald Trump: I Have a Big D***

Donald Trump went after Marco Rubio for insinuating he came up short below the belt, telling a crowd Thursday night, he has a big ol' penis.

Trump squared off with his opponents at the latest Republican debate, and right out of the box addressed Rubio's barb, "And you know what they say about men with small hands. You Can't trust them."

Trump made it clear ... he's big where it counts, hands down.