What does X mean as pin state?

[Oaklander]

On the 4th page of LTC1483 datasheet there is a function table.
The state of the RE pin is marked as X when the device is configured to transmitting. What does it mean?

I've prototyped the a circuit containing this chip with RE connected to ground and it worked. Now I'm desgining a PCB and don't want to do anything stupid so I'd like to know exactly what the X means.

[sokoloff]

It means "anything; this pin has no effect on this line"

[Brumby]

I was going to say "it doesn't matter".

[Cerebus]

If it's an output it means "undefined", meaning that you cannot and should not rely on the state of that pin with the device in that mode/state/configuration. If it's an input it is "don't care" and that pin will have no effect (is ignored), no matter what state the pin is in, with the device in that mode/state/configuration.

[Oaklander]

Thank you all. That was quick.