Yes, square is playable
...and is worth 16 points.
Found in the following dictionaries
Enable (Words with friends)
SOWPODS (Collins Scrabble Words)
OTCWL2014 (NASPA Word List 2014)
TWL06 (NASPA List 2006)
"Square" Definition
noun
A plane figure having four equal sides.
A rectangular space enclosed by streets and occupied by buildings; a block.
A T-shaped or L-shaped instrument for drawing or testing right angles.
An open, usually four-sided area at the intersection of two or more streets, often planted with grass and trees for use as a park.
Games Any of the quadrilateral spaces on a board, as in chess.
verb
To make square or rectangular .
To test for deviation from a right angle, straight line, or plane surface.
To bring approximately to a right angle .
To multiply (a number) by itself raise to the second power.
To find a square equal in area to .
adjective
Approximately rectangular and equilateral in cross section: a square house.
Characterized by blocklike solidity or sturdiness.
Expressed in units measuring area: square feet.
Having a base that is a square: a square pyramid.
adverb
Directly; straight: ran square into each other.
In a solid manner; firmly.
In an honest, straightforward manner.
Mathematics At right angles.
verb-transitive
Informal To bribe or fix: a party in litigation that tried to square the judge.
Mathematics To find a square equal in area to (the area of a given figure).
Mathematics To raise (a number or quantity) to the second power.
Sports To even the score of: to square a game.
To bring (oneself) into a better position or relation: He tried to square himself with his parents.
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