1) To bum around, to do nothing, to be lazy.
2) A bizarre sexual practise where the male wheezes uncontrolably whilst attempting to suck his own penis.
3) To bite someone's knee whilst having doggy-style sex. This can also be used for foreplay on an unwilling person.
2) "I was kept up all night by my room mate naiffing"
3) "Oh baby, let me naiff you!" or "Stay away from him, he looks like a naiffer"