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.
1) "Come on man, you gotta get a job - don't be a naiff!"
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"