Is frosting a word in the Scrabble Dictionary

Yes, frosting is playable

...and is worth 14 points.

Found in the following dictionaries

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

"Frosting" Definition

noun

A roughened or speckled surface imparted to glass or metal.
Icing, as on a cake.
Lusterless finish of metal or glass .
A white finish produced on glass (as by etching).
The lightening (as by chemicals) of small strands of hair throughout the entire head to produce a two-tone effect .