hijack vs carjack

hijack is a noun but carjack is not a noun.

Word	Noun	Adjective	Verb	Adverb
hijack	Yes	No	Yes	No
carjack	No	No	Yes	No

As verbs, carjack is a hyponym of hijack; that is, carjack is a word with a more specific, narrower meaning than hijack:

hijack: take arbitrarily or by force
carjack: take someone's car from him by force, usually with the intention of stealing it

Other hyponyms of hijack include skyjack.

hijack (noun)	carjack (noun)
seizure of a vehicle in transit either to rob it or divert it to an alternate destination

hijack (verb)	carjack (verb)
take arbitrarily or by force	take someone's car from him by force, usually with the intention of stealing it
seize control of