Yes, TIGERS is a Scrabble word!

Letter values in Scrabble US: T 1, I 1, G 2, E 1, R 1, S 1.

Is it a valid word?

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

a terrorist organization in Sri Lanka that began in 1970 as a student protest over the limited university access for Tamil students; currently seeks to establish an independent Tamil state called Eelam; relies on guerilla strategy including terrorist tactics that target key government and military personnel
a fierce or audacious person
large feline of forests in most of Asia having a tawny coat with black stripes; endangered

Also: liberation tigers of tamil eelam, tamil tigers, world tamil association, world tamil movement, panthera tigris.

Not playable in Scrabble US: LTTE.