Is rumba a word in the Scrabble Dictionary

Yes, rumba 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)

"Rumba" Definition

noun

A dance of Cuban origin, combining complex footwork with a pronounced movement of the hips.
A modern ballroom adaptation of this dance.
Music for this dance or in this style.
A ballroom dance of Cuban origin in or time with a basic pattern of step-close-step and marked by a delayed transfer of weight and pronounced hip movements.
The music for this dance.