A cute synonym for (full-contact) kissing*, useful if you want to talk
about kissing directly, if conversing with your S.O. in the company of
friends or as a plausible excuse for phoning in sick when really you want to
phone in well - "...won't be coming in today he's stained his osculatory
muscles and can't get to the phone right now".
Also used in the song (as as the title for the album containing the same) -
'Osculate Me Baby' by blues/jazz singer Etta James.
nice work if you can get it
*Strictly speaking it implies full use of the lips though not necessarily
tongues - not the kind of thing you would do with your mother anyway.