The Collaborative International Dictionary of English v.0.48:

Np \Np\ n.
   The chemical symbol for Neptunium, a transuranic element
   having atomic number 93.

   Syn: Neptunium, atomic number 93.
        [WordNet 1.5]

V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

NP
       No Problem (telecommunication, Usenet, IRC)


V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

NP
       Network Performance


The Jargon File (version 4.4.7, 29 Dec 2003):

NP-
 /N?P/, pref.

    Extremely. Used to modify adjectives describing a level or quality of
    difficulty; the connotation is often ?more so than it should be?. This is
    generalized from the computer-science terms NP-hard and NP-complete;
    NP-complete problems all seem to be very hard, but so far no one has found
    a proof that they are. NP is the set of Nondeterministic-Polynomial
    problems, those that can be completed by a nondeterministic Turing machine
    in an amount of time that is a polynomial function of the size of the
    input; a solution for one NP-complete problem would solve all the others. ?
    Coding a BitBlt implementation to perform correctly in every case is
    NP-annoying.?

    Note, however, that strictly speaking this usage is misleading; there are
    plenty of easy problems in class NP. NP-complete problems are hard not
    because they are in class NP, but because they are the hardest problems in
    class NP.