Yes, SIDE is a Scrabble word!

Letter values in Scrabble US: S 1, I 1, D 2, E 1.

Is it a valid word?

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

a place within a region identified relative to a center or reference location
one of two or more contesting groups
either the left or right half of a body
a surface forming part of the outside of an object
an extended outer surface of an object
an aspect of something (as contrasted with some other implied aspect)
a line segment forming part of the perimeter of a plane figure
a family line of descent
a lengthwise dressed half of an animal's carcass used for food
an opinion that is held in opposition to another in an argument or dispute
an elevated geological formation
(sports) the spin given to a ball by striking it on one side or releasing it with a sharp twist

Also: side of meat.