highjacker vs highwayman

highjacker and highwayman both are nouns.

Word	Noun	Adjective	Verb	Adverb
highjacker	Yes	No	No	No
highwayman	Yes	No	No	No

As nouns, highjacker and highwayman are synonyms defined as:

highjacker and highwayman: a holdup man who stops a vehicle and steals from it

Other synonyms of highjacker include hijacker, road agent.

highjacker (noun)	highwayman (noun)
a holdup man who stops a vehicle and steals from it	a holdup man who stops a vehicle and steals from it
someone who uses force to take over a vehicle (especially an airplane) in order to reach an alternative destination