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.
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.
verb
To pass from physical life .
To pass out of existence .
To disappear or subside gradually .
To long keenly or desperately .
To be overwhelmed by emotion .
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.