Yes, DISCOURTESY is a Scrabble word!

Letter values in Scrabble US: D 2, I 1, S 1, C 3, O 1, U 1, R 1, T 1, E 1, S 1, Y 4.

Is it a valid word?

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

an expression of lack of respect
a manner that is rude and insulting
a lack of politeness; a failure to show regard for others; wounding the feelings or others

Also: offensive activity.