Yes, die is playable
...and is worth 4 points.
Found in the following dictionaries
Enable (Words with friends)
SOWPODS (Collins Scrabble Words)
OTCWL2014 (NASPA Word List 2014)
TWL06 (NASPA List 2006)
"Die" Definition
noun
A device used for cutting out, forming, or stamping material, especially:.
A game of chance using dice.
A metal block containing small conical holes through which plastic, metal, or other ductile material is extruded or drawn.
A part on a machine that punches shaped holes in, cuts, or forms sheet metal, cardboard, or other stock.
A small cube marked on each side with from one to six dots, usually used in pairs in gambling and in various other games.
phrasal-verb
Die back Botany To be affected by dieback.
Die down To lose strength; subside: The winds died down.
Die off To undergo a sudden, sharp decline in population: Rabbits were dying off in that county.
Die out To cease living completely; become extinct: tribes and tribal customs that died out centuries ago.
idiom
Die hard To resist against overwhelming, hopeless odds: radicalism that dies hard.
Die hard To take a long time in passing out of existence: racial prejudices that die hard.
Die on the vine To fail, as from lack of support, especially at an early stage: a plan that died on the vine.
Load the dice To make an outcome highly probable; predetermine a result: "These factors merely load the dice, upping the odds that a household will fall into a certain . . . income distribution” ( Thomas G. Exter).
Load the dice To put another at a distinct disadvantage, as through prior maneuver: The dice were loaded against the defendant before the trial.
verb-intransitive
Informal To desire something greatly: I am dying for a box of chocolates. She was dying to see the exhibit.
To be destroyed, as in combat: could see the remains of two aircraft that had died in the attack.
To become indifferent: had died to all worldly concerns.
To cease existing, especially by degrees; fade: The sunlight died in the west.
To cease living; become dead; expire.
verb-transitive
To cut, form, or stamp with or as if with a die.