Stands for "Emergency No Internet Porn." Usually collected in a folder, ENIP is for chronic masturbaters who, for some reason or another, can use their computer, but cannot use the internet.
ENIP usually consists of various lewd pictures or videos, saved in a "discreet" folder.
"Yo, dude, my internet was out last night, so I had to use my ENIP to get one off."
"Holy shit. My ENIP folder is bulging with all of the best porn."