highwayman vs hijacker

highwayman and hijacker both are nouns.

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

As nouns, highwayman and hijacker are synonyms defined as:

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

Other synonyms of highwayman include highjacker, road agent.

highwayman (noun)	hijacker (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