The expression (getting or going to) third base is slang for sexual contact with genitals, especially when it happens for the first time between two people. The expression (being) born on third base refers to having advantages in life by virtue of being born into wealth and other privileges.

What means second base?

1 : the base that must be touched second by a base runner in baseball. 2 : the player position for defending the area on the first-base side of second base. Other Words from second base Example Sentences Learn More About second base.