Yes, BACKBONE is a Scrabble word!

Letter values in Scrabble US: B 3, A 1, C 3, K 5, B 3, O 1, N 1, E 1.

Is it a valid word?

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

a central cohesive source of support and stability
fortitude and determination
the series of vertebrae forming the axis of the skeleton and protecting the spinal cord
the part of a book's cover that encloses the inner side of the book's pages and that faces outward when the book is shelved
the part of a network that connects other networks together

Also: spinal column, vertebral column.