Is hijack a word in the Scrabble Dictionary

Yes, hijack is playable

...and is worth 24 points.

Found in the following dictionaries

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

"Hijack" Definition

noun

The act or an instance of hijacking.

verb-transitive

To seize control of (a moving vehicle) by use of force, especially in order to reach an alternate destination.
To steal (goods) from a vehicle in transit.
To steal from as if by hijacking.
To stop and rob (a vehicle in transit).
To swindle or subject to extortion.

verb

To steal by stopping a vehicle on the highway.
To commandeer (a flying airplane) especially by coercing the pilot at gunpoint.
To stop and steal from (a vehicle in transit).
To steal or rob as if by.
To subject to extortion or swindling.