1) The large wooly mammoth featured on the children's television program, Sesame Street. He could only be seen by Big Bird
2) A person or thing that either exists only in one's mind or others have never met, therefore think only exists in one's mind.
The act of a man placing one's testicles over a woman's eyes and flopping his penis over her nose; resembling the bug-eyed character from Sesame Street.
A boyfriend or girlfriend in which no one has ever met. The supposed occurance of snuffaluffagi has been dramaticaly increasing due to the popularity of long distance internet dating.
Bob: "Man I hardly ever see Dan anymore since he started seeing that new girl and no one has ever met her. I think he is datig a snuffaluffagus"