Is strait a word in the Scrabble Dictionary

Yes, strait 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)

"Strait" Definition

noun

A narrow channel joining two larger bodies of water. Often used in the plural with a singular verb.
A position of difficulty, perplexity, distress, or need. Often used in the plural: in desperate straits.
A situation of perplexity or distress .
A comparatively narrow passageway connecting two large bodies of water .
A narrow space or passage.

adjective

Archaic Affording little space or room; confined.
Archaic Fitting tightly; constricted.
Archaic Narrow.
Archaic Strict, rigid, or righteous.
Difficult; stressful.

adverb

In a close or tight manner.