onanism vs frottage

onanism and frottage both are nouns.

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

As nouns, frottage is a hyponym of onanism; that is, frottage is a word with a more specific, narrower meaning than onanism:

onanism: manual stimulation of the genital organs (of yourself or another) for sexual pleasure
frottage: masturbation by rubbing against another person (as in a crowd)

Other hyponyms of onanism include self-abuse, self-stimulation, hand job, jacking off, jerking off, wank.

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a method of birth control in which coitus is initiated but the penis is deliberately withdrawn before ejaculation