Yes, arm is playable
...and is worth 6 points.
Found in the following dictionaries
Enable (Words with friends)
SOWPODS (Collins Scrabble Words)
OTCWL2014 (NASPA Word List 2014)
TWL06 (NASPA List 2006)
"Arm" Definition
noun
A branch of a military force: infantry, armor, and other combat arms.
A part similar to a human arm, such as the forelimb of an animal or a long part projecting from a central support in a machine.
A relatively narrow extension jutting out from a large mass: an arm of the sea. See Synonyms at branch.
A weapon, especially a firearm: troops bearing arms; ICBMs, bombs, and other nuclear arms.
An administrative or functional branch, as of an organization.
idiom
An arm and a leg Slang An excessively high price: a cruise that cost an arm and a leg.
Arm in arm With arms linked together: They walked across the beach arm in arm.
Up in arms Extremely upset; indignant.
With open arms With great cordiality and hospitality.
verb-transitive
To equip with weapons: armed themselves with loaded pistols; arm a missile with a warhead; arm a nation for war.
To equip with what is needed for effective action: tax advisers who were armed with the latest forms.
To prepare (a weapon) for use or operation, as by releasing a safety device.
To provide with something that strengthens or protects: a space reentry vehicle that was armed with a ceramic shield.
verb-intransitive
To prepare oneself for warfare or conflict.
To supply or equip oneself with weaponry.
abbreviation
Adjustable rate mortgage.
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