osculation vs soul kiss

osculation and soul kiss both are nouns.

Word	Noun	Adjective	Verb	Adverb
osculation	Yes	No	No	No
soul kiss	Yes	No	No	No

As nouns, soul kiss is a hyponym of osculation; that is, soul kiss is a word with a more specific, narrower meaning than osculation:

osculation: the act of caressing with the lips (or an instance thereof)
soul kiss: an openmouthed kiss in which your tongue is inserted into the other's mouth

Other hyponyms of osculation include smack, smooch, deep kiss, French kiss, peck.

osculation (noun)	soul kiss (noun)
the act of caressing with the lips (or an instance thereof)	an openmouthed kiss in which your tongue is inserted into the other's mouth
(mathematics) a contact of two curves (or two surfaces) at which they have a common tangent