seizer vs kidnapper

seizer and kidnapper both are nouns.

Word	Noun	Adjective	Verb	Adverb
seizer	Yes	No	No	No
kidnapper	Yes	No	No	No

As nouns, kidnapper is a hypernym of seizer; that is, kidnapper is a word with a broader meaning than seizer:

seizer: a kidnapper who drugs men and takes them for compulsory service aboard a ship
kidnapper: someone who unlawfully seizes and detains a victim (usually for ransom)

Other hypernyms of seizer include abductor, kidnaper, snatcher.

seizer (noun)	kidnapper (noun)
a kidnapper who drugs men and takes them for compulsory service aboard a ship	someone who unlawfully seizes and detains a victim (usually for ransom)