wank vs onanism

wank and onanism both are nouns.

Word	Noun	Adjective	Verb	Adverb
wank	Yes	No	Yes	No
onanism	Yes	No	No	No

As nouns, onanism is a hypernym of wank; that is, onanism is a word with a broader meaning than wank:

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

Other hypernyms of wank include masturbation.

wank (noun)	onanism (noun)
slang for masturbation	manual stimulation of the genital organs (of yourself or another) for sexual pleasure
	a method of birth control in which coitus is initiated but the penis is deliberately withdrawn before ejaculation

wank (verb)	onanism (verb)
get sexual gratification through self-stimulation