You guys have it all wrong.
Snogging is when you are cuddled together and one of you giggles, and then starts snorting. This makes the other one laugh and they start snorting too.
--pretty soon the two of you sound like a pair of piggies rooting in the mud.
Its pretty innocent, but the sound grosses other people out. Hence the phrase, "Get a room!" was born.
Now in older men, it often gets wrongly applied. They can get in romantic situation, start giggling and let go a series of farts. But the older woman stops laughing, slugs him, and kicks him outa bed. This led to the invention of the couch. But don't be misled, this isn't snogging at all.