jacking off vs masturbation

jacking off and masturbation both are nouns.

Word	Noun	Adjective	Verb	Adverb
jacking off	Yes	No	No	No
masturbation	Yes	No	No	No

As nouns, masturbation is a hypernym of jacking off; that is, masturbation is a word with a broader meaning than jacking off:

jacking off: slang for masturbation
masturbation: manual stimulation of the genital organs (of yourself or another) for sexual pleasure

Other hypernyms of jacking off include onanism.

jacking off (noun)	masturbation (noun)
slang for masturbation	manual stimulation of the genital organs (of yourself or another) for sexual pleasure