Yes, PILLARS is a Scrabble word!

Letter values in Scrabble US: P 3, I 1, L 1, L 1, A 1, R 1, S 1.

Is it a valid word?

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

a fundamental principle or practice
anything that approximates the shape of a column or tower
a prominent supporter
a vertical cylindrical structure standing alone and not supporting anything (such as a monument)
(architecture) a tall vertical cylindrical structure standing upright and used to support a structure