when one "hugs" another with one's tongues. In other words, making out with your tongues. Also known as, French Kiss.
Man, that Katie sure gave me a nice slug hug. It was wet, sloppy and DELICIOUS.
The male equivelant to camel toe. When well endowed scenesters wear tight jeans and tight boxers, or when professional wrestlers strut their stuff in nothing but tighty whities, the slug hug is evident to all.
Aw man, check out that emo kid's slug hug. He'll be getting lucky.