what does it mean when someone says a car has xxx 'original' miles? is there such a thing as un-original miles?

sure.

the dash could have been replaced

engine

trans

or even someone turning back the miles manually.

other than that, umm...i guess they just mean that the miles are correct? or they just think its a good selling point?

I can be defined in many ways, to me it would mean that the mileage on the odometer is the true mileage with the original motor and trany set up. In other words, what you see is what is there.
In some cases, when people change the motor they reset the odometer, which can be considered a no no.

LOL, kinda like when the Captain comes over the intercom and says they are ready to make the FINAL approach, gee whiz, how many approaches have they tried so far?

It all depends on how its written. For example, if I am selling my car and I know it has 190K on the clock, some will write it as 190,xxx which means that they do not know the exact mileage as of the posting time but gives a general idea that it has 190+K miles on it.

I don't think he'* questioning the "xxx" part. it'* the "Original" part that'* in question.

Face it, some of drive the same miles over and over again, thus my car has just over 57 original miles, but due to the number of times I've driven those miles....

Oh Ok.......

I believe it'* a throwback from the days when odometers only had 6 digits...when you hit 99,999.9 miles, that was the last of your "original" miles and the ODMeter rolled back to 00000.0. Consequently, when you had a 5 year old car with 5,000 miles on it you'd say they were original miles to inform potential buyers that the car didn't have 105,000 miles. That way they would know you're a liar.

Like an "adult owned" car?

I'm 19. I'm an adult. If I were selling my car, it surely would be "adult owned"