a slang term for "nice", used interchangeably with "sweet" or "cool". Usually drawn out in speech and pronounced "n iiiiiii eeeeee"
Mike: "Dude those are some niii pics you got there from your backpacking trip."
Teacher: "No homework this weekend, class."
Student: "Niiiiiiiii!"
Teacher: "No homework this weekend, class."
Student: "Niiiiiiiii!"
by Cruel Leader March 02, 2010