Yes, wall is playable
...and is worth 9 points.
Found in the following dictionaries
Enable (Words with friends)
SOWPODS (Collins Scrabble Words)
OTCWL2014 (NASPA Word List 2014)
TWL06 (NASPA List 2006)
"Wall" Definition
noun
A continuous structure of masonry or other material forming a rampart and built for defensive purposes. Often used in the plural.
A structure of stonework, cement, or other material built to retain a flow of water.
An extreme or desperate condition or position, such as defeat or ruin: driven to the wall by poverty.
An upright structure of masonry, wood, plaster, or other building material serving to enclose, divide, or protect an area, especially a vertical construction forming an inner partition or exterior siding of a building.
Something resembling a wall in appearance, function, or construction, as the exterior surface of a body organ or part: the abdominal wall.
idiom
Off the wall Slang Extremely unconventional.
Off the wall Slang Without foundation; ridiculous: an accusation that is really off the wall.
Up the wall Slang Into a state of extreme frustration, anger, or distress: tensions that are driving me up the wall.
Writing An ominous indication of the course of future events: saw the writing on the wall and fled the country.
verb-transitive
To block or close (an opening or passage, for example) with or as if with a wall.
To confine or seal behind a wall; immure: "I determined to wall [the body] up in the cellar” ( Edgar Allan Poe).
To divide or separate with or as if with a wall. Often used with off: wall off half a room.
To enclose, surround, or fortify with or as if with a wall: wall up an old window. See Synonyms at enclose.
verb
To provide, cover with, or surround with or as if with a wall.
To separate by or as if by a wall.
To close (an opening) with or as if with a wall.
To roll in a dramatic manner.
To roll (one's eyes) in a dramatic manner.