Yes, DISTORTION is a Scrabble word!

Letter values in Scrabble US: D 2, I 1, S 1, T 1, O 1, R 1, T 1, I 1, O 1, N 1.

Is it a valid word?

DISTORTION is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a change for the worse
a shape resulting from distortion
an optical phenomenon resulting from the failure of a lens or mirror to produce a good image
a change (usually undesired) in the waveform of an acoustic or analog electrical signal; the difference between two measurements of a signal (as between the input and output signal)
the act of distorting something so it seems to mean something it was not intended to mean
the mistake of misrepresenting the facts

Also: distorted shape, optical aberration.