onanism vs masturbation

onanism and masturbation both are nouns.

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

As nouns, onanism and masturbation are synonyms defined as:

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

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a method of birth control in which coitus is initiated but the penis is deliberately withdrawn before ejaculation