Is tutti a word in the Scrabble Dictionary

Yes, tutti is playable

...and is worth 6 points.

Found in the following dictionaries

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

"Tutti" Definition

noun

A passage of ensemble music intended to be executed by all the performers simultaneously.
An ensemble of musicians, in contrast to a solist or group of solists, in a concerto.
A passage or section performed by all the performers.

adverb

All. Used chiefly as a direction to indicate that all performers are to take part.

adjective or adverb

With all voices or instruments performing together.