Yes, back is playable
...and is worth 14 points.
Found in the following dictionaries
Enable (Words with friends)
SOWPODS (Collins Scrabble Words)
OTCWL2014 (NASPA Word List 2014)
TWL06 (NASPA List 2006)
"Back" Definition
noun
A part that supports or strengthens from the rear: the back of a couch.
A shallow vat or tub used chiefly by brewers.
Sports A player who takes a position behind the front line of other players in certain games, such as football and soccer.
Sports This playing position.
The analogous dorsal region in other animals.
verb
To support by material or moral assistance.
To assume financial responsibility for.
To provide musical accompaniment for.
To cause to go back or in reverse.
To articulate (a sound) with the tongue farther back.
geographical name
River 605 (974 ) Canada in Nunavut rising along border with Northwest Territories & flowing into Arctic Ocean.
adverb
At, to, or toward the rear or back; backward.
In check or under restraint: Barriers held the crowd back.
In reserve or concealment.
In, to, or toward a former condition.
idiom
Back and fill Nautical To maneuver a vessel in a narrow channel by adjusting the sails so as to let the wind in and out of them in alteration.
Back to back Consecutively and without interruption: presented three speeches back to back.
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