kissing vs petting

kissing and petting both are nouns.

Word	Noun	Adjective	Verb	Adverb
kissing	Yes	No	No	No
petting	Yes	No	No	No

As nouns, kissing and petting are synonyms defined as:

kissing and petting: affectionate play (or foreplay without contact with the genital organs)

Other synonyms of kissing include caressing, cuddling, fondling, hugging, necking, smooching, snuggling.

kissing (noun)	petting (noun)
affectionate play (or foreplay without contact with the genital organs)	affectionate play (or foreplay without contact with the genital organs)