Is wham a word in the Scrabble Dictionary

Yes, wham is playable

...and is worth 12 points.

Found in the following dictionaries

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

"Wham" Definition

noun

A forceful, resounding blow.
The sound of such a blow; a thud.
A solid blow.
The loud sound of a hard impact.

verb-intransitive

To smash with great force.

verb-transitive

To strike or smash into with resounding impact.

adverb

With violent abruptness.

verb

To propel, strike, or beat so as to produce a loud impact.
To hit or explode with a loud impact.