Source : WordNet®

Nb
     n 1: a soft gray ductile metallic element used in alloys; occurs
          in niobite; formerly called columbium [syn: {niobium}, {atomic
          number 41}]
     2: a Latin phrase (or its abbreviation) used to indicate that
        special attention should be paid to something; "the
        margins of his book were generously supplied with
        pencilled NBs" [syn: {nota bene}, {N.B.}]

Source : Free On-Line Dictionary of Computing

NB
     
        {C}