Is borax a word in the Scrabble Dictionary

Yes, borax is playable

...and is worth 15 points.

Found in the following dictionaries

Enable (Words with friends)
SOWPODS (Collins Scrabble Words)
OTCWL2014 (NASPA Word List 2014)
TWL06 (NASPA List 2006)

"Borax" Definition

noun

A hydrated sodium borate, Na2B4O7·10H2O, an ore of boron, that is used as a cleaning compound.
An anhydrous sodium borate used in the manufacture of glass and various ceramics.
A white crystalline compound that consists of a hydrated sodium NaBO·10HO, that occurs as a mineral or is prepared from other minerals, and that is used especially as a flux, cleansing agent, and water softener, as a preservative, and as a fireproofing agent.
Cheap shoddy merchandise.
Good-natured teasing or ridicule; banter:.