Since you were on Wikipedia anyway: Type safety.
Type safety means, roughly speaking, that the language prohibits you from accidentally mixing up your types.
memcpy is not type-safe because you can easily copy the memory of some int into a char array and end up with meaningless data. printf is not type safe because you can provide a %i format specifier with a string; again, the string will be interpreted as an int and you'll end up with garbage. (Incidentally, the VC++ compiler does check the format string in some situations.)
std::vector is type-safe, because it only allows you to put values of the given type T into it. (You can do explicit typecasts, of course, but the point is that you have to be explicit about doing something that's not type safe).
